diff --git a/doc/manual/rl-next/json-format-changes.md b/doc/manual/rl-next/json-format-changes.md
index e264daf04..78e543512 100644
--- a/doc/manual/rl-next/json-format-changes.md
+++ b/doc/manual/rl-next/json-format-changes.md
@@ -49,17 +49,10 @@ The new structured format follows the [JSON guidelines](@docroot@/development/js
   Content address is now a structured JSON object instead of a string:
 
   - Old: `"ca": "fixed:r:sha256:1abc..."`
-  - New: `"ca": {"method": "nar", "hash": {"algorithm": "sha256", "format": "base16", "hash": "10c209fa..."}}`
+  - New: `"ca": {"method": "nar", "hash": "sha256-ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0="}`
   - Still `null` values for input-addressed store objects
 
-- **Structured hash fields**:
-
-  Hash values (`narHash` and `downloadHash`) are now structured JSON objects instead of strings:
-
-  - Old: `"narHash": "sha256:FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc="`
-  - New: `"narHash": {"algorithm": "sha256", "format": "base16", "hash": "15e3c5608946..."}`
-  - Same structure applies to `downloadHash` in NAR info contexts
-  - The `format` field is always `"base16"` (hexadecimal)
+  The `hash` field uses the [SRI](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity) format like other hashes.
 
 Nix currently only produces, and doesn't consume this format.
 
diff --git a/doc/manual/source/protocols/json/hash.md b/doc/manual/source/protocols/json/hash.md
index f2af5303f..3ecff4da0 100644
--- a/doc/manual/source/protocols/json/hash.md
+++ b/doc/manual/source/protocols/json/hash.md
@@ -5,13 +5,13 @@
 ### SHA-256
 
 ```json
-{{#include schema/hash-v1/sha256-base16.json}}
+{{#include schema/hash-v1/sha256.json}}
 ```
 
 ### BLAKE3
 
 ```json
-{{#include schema/hash-v1/blake3-base16.json}}
+{{#include schema/hash-v1/blake3.json}}
 ```
 
 <!-- need to convert YAML to JSON first
diff --git a/doc/manual/source/protocols/json/schema/hash-v1.yaml b/doc/manual/source/protocols/json/schema/hash-v1.yaml
index 762f67021..c7e46191d 100644
--- a/doc/manual/source/protocols/json/schema/hash-v1.yaml
+++ b/doc/manual/source/protocols/json/schema/hash-v1.yaml
@@ -4,36 +4,13 @@ title: Hash
 description: |
   A cryptographic hash value used throughout Nix for content addressing and integrity verification.
 
-  This schema describes the JSON representation of Nix's `Hash` type.
-type: object
-properties:
-  algorithm:
-    "$ref": "#/$defs/algorithm"
-  format:
-    type: string
-    enum:
-    - base16
-    title: Hash format
-    description: |
-      The encoding format of the hash value.
+  This schema describes the JSON representation of Nix's `Hash` type as an [SRI](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity) string.
+type: string
+pattern: "^(blake3|md5|sha1|sha256|sha512)-[A-Za-z0-9+/]+=*$"
+examples:
+- "sha256-ungWv48Bz+pBQUDeXa4iI7ADYaOWF3qctBD/YfIAFa0="
+- "sha512-IEqPxt2oLwoM7XvrjgikFlfBbvRosiioJ5vjMacDwzWW/RXBOxsH+aodO+pXeJygMa2Fx6cd1wNU7GMSOMo0RQ=="
 
-      `base16` (lowercase hexadecimal) is the only format that is currently supported for JSON serialization.
-      This field exists primarily to reduce ambiguity about what the hash means.
-      It would also help us support other formats in the future, but there are no concrete plans to do so at this.
-  hash:
-    type: string
-    title: Hash
-    description: |
-      The encoded hash value, itself.
-
-      It is specified in the format specified by the `format` field.
-      It must be the right length for the hash algorithm specified in the `algorithm` field, also.
-      The hash value does not include any algorithm prefix.
-required:
-- algorithm
-- format
-- hash
-additionalProperties: false
 "$defs":
   algorithm:
     type: string
diff --git a/src/json-schema-checks/meson.build b/src/json-schema-checks/meson.build
index 1a30ec424..20acfe411 100644
--- a/src/json-schema-checks/meson.build
+++ b/src/json-schema-checks/meson.build
@@ -32,8 +32,8 @@ schemas = [
     'stem' : 'hash',
     'schema' : schema_dir / 'hash-v1.yaml',
     'files' : [
-      'sha256-base16.json',
-      'blake3-base16.json',
+      'sha256.json',
+      'blake3.json',
     ],
   },
   {
diff --git a/src/libstore-tests/data/common-protocol/content-address.json b/src/libstore-tests/data/common-protocol/content-address.json
index 674c5cc68..3c63e6d9b 100644
--- a/src/libstore-tests/data/common-protocol/content-address.json
+++ b/src/libstore-tests/data/common-protocol/content-address.json
@@ -1,26 +1,14 @@
 [
   {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "f9773d2e5ea670f96dc1a7b0ae4fc1010e7a6371b94ffff0ce1294734ceb62ed"
-    },
+    "hash": "sha256-+Xc9Ll6mcPltwaewrk/BAQ56Y3G5T//wzhKUc0zrYu0=",
     "method": "text"
   },
   {
-    "hash": {
-      "algorithm": "sha1",
-      "format": "base16",
-      "hash": "8067a60687a7562359337862c2a9ecfc5833ab0a"
-    },
+    "hash": "sha1-gGemBoenViNZM3hiwqns/Fgzqwo=",
     "method": "flat"
   },
   {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   }
 ]
diff --git a/src/libstore-tests/data/common-protocol/optional-content-address.json b/src/libstore-tests/data/common-protocol/optional-content-address.json
index dc7d7d525..1c57fbf25 100644
--- a/src/libstore-tests/data/common-protocol/optional-content-address.json
+++ b/src/libstore-tests/data/common-protocol/optional-content-address.json
@@ -1,11 +1,7 @@
 [
   null,
   {
-    "hash": {
-      "algorithm": "sha1",
-      "format": "base16",
-      "hash": "8067a60687a7562359337862c2a9ecfc5833ab0a"
-    },
+    "hash": "sha1-gGemBoenViNZM3hiwqns/Fgzqwo=",
     "method": "flat"
   }
 ]
diff --git a/src/libstore-tests/data/content-address/nar.json b/src/libstore-tests/data/content-address/nar.json
index af61d7e43..511cb1c5c 100644
--- a/src/libstore-tests/data/content-address/nar.json
+++ b/src/libstore-tests/data/content-address/nar.json
@@ -1,8 +1,4 @@
 {
-  "hash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "f6f2ea8f45d8a057c9566a33f99474da2e5c6a6604d736121650e2730c6fb0a3"
-  },
+  "hash": "sha256-9vLqj0XYoFfJVmoz+ZR02i5camYE1zYSFlDicwxvsKM=",
   "method": "nar"
 }
diff --git a/src/libstore-tests/data/content-address/text.json b/src/libstore-tests/data/content-address/text.json
index a5636fe02..96da7874c 100644
--- a/src/libstore-tests/data/content-address/text.json
+++ b/src/libstore-tests/data/content-address/text.json
@@ -1,8 +1,4 @@
 {
-  "hash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "f0e4c2f76c58916ec258f246851bea091d14d4247a2fc3e18694461b1816e13b"
-  },
+  "hash": "sha256-8OTC92xYkW7CWPJGhRvqCR0U1CR6L8PhhpRGGxgW4Ts=",
   "method": "text"
 }
diff --git a/src/libstore-tests/data/derivation/output-caFixedFlat.json b/src/libstore-tests/data/derivation/output-caFixedFlat.json
index 0c1e8b017..86b4d2029 100644
--- a/src/libstore-tests/data/derivation/output-caFixedFlat.json
+++ b/src/libstore-tests/data/derivation/output-caFixedFlat.json
@@ -1,8 +1,4 @@
 {
-  "hash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "894517c9163c896ec31a2adbd33c0681fd5f45b2c0ef08a64c92a03fb97f390f"
-  },
+  "hash": "sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8=",
   "method": "flat"
 }
diff --git a/src/libstore-tests/data/derivation/output-caFixedNAR.json b/src/libstore-tests/data/derivation/output-caFixedNAR.json
index 8963d3191..6f9654572 100644
--- a/src/libstore-tests/data/derivation/output-caFixedNAR.json
+++ b/src/libstore-tests/data/derivation/output-caFixedNAR.json
@@ -1,8 +1,4 @@
 {
-  "hash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "894517c9163c896ec31a2adbd33c0681fd5f45b2c0ef08a64c92a03fb97f390f"
-  },
+  "hash": "sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8=",
   "method": "nar"
 }
diff --git a/src/libstore-tests/data/derivation/output-caFixedText.json b/src/libstore-tests/data/derivation/output-caFixedText.json
index 78c09adb7..2611e75da 100644
--- a/src/libstore-tests/data/derivation/output-caFixedText.json
+++ b/src/libstore-tests/data/derivation/output-caFixedText.json
@@ -1,8 +1,4 @@
 {
-  "hash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "894517c9163c896ec31a2adbd33c0681fd5f45b2c0ef08a64c92a03fb97f390f"
-  },
+  "hash": "sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8=",
   "method": "text"
 }
diff --git a/src/libstore-tests/data/dummy-store/one-flat-file.json b/src/libstore-tests/data/dummy-store/one-flat-file.json
index a3f6bdcf3..804bbf07d 100644
--- a/src/libstore-tests/data/dummy-store/one-flat-file.json
+++ b/src/libstore-tests/data/dummy-store/one-flat-file.json
@@ -12,19 +12,11 @@
       },
       "info": {
         "ca": {
-          "hash": {
-            "algorithm": "sha256",
-            "format": "base16",
-            "hash": "7f579dbae488602d41a1f5c0d6dc9c17bf408b635230942d504af1e43c4b6125"
-          },
+          "hash": "sha256-f1eduuSIYC1BofXA1tycF79Ai2NSMJQtUErx5DxLYSU=",
           "method": "nar"
         },
         "deriver": null,
-        "narHash": {
-          "algorithm": "sha256",
-          "format": "base16",
-          "hash": "7f579dbae488602d41a1f5c0d6dc9c17bf408b635230942d504af1e43c4b6125"
-        },
+        "narHash": "sha256-f1eduuSIYC1BofXA1tycF79Ai2NSMJQtUErx5DxLYSU=",
         "narSize": 120,
         "references": [],
         "registrationTime": null,
diff --git a/src/libstore-tests/data/nar-info/json-2/impure.json b/src/libstore-tests/data/nar-info/json-2/impure.json
index acc458d33..b7b9f5118 100644
--- a/src/libstore-tests/data/nar-info/json-2/impure.json
+++ b/src/libstore-tests/data/nar-info/json-2/impure.json
@@ -1,25 +1,13 @@
 {
   "ca": {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   },
   "compression": "xz",
   "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-  "downloadHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "downloadHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "downloadSize": 4029176,
-  "narHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
   "references": [
     "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
diff --git a/src/libstore-tests/data/nar-info/json-2/pure.json b/src/libstore-tests/data/nar-info/json-2/pure.json
index 452d83361..0350349a9 100644
--- a/src/libstore-tests/data/nar-info/json-2/pure.json
+++ b/src/libstore-tests/data/nar-info/json-2/pure.json
@@ -1,17 +1,9 @@
 {
   "ca": {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   },
-  "narHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
   "references": [
     "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
diff --git a/src/libstore-tests/data/path-info/json-2/empty_impure.json b/src/libstore-tests/data/path-info/json-2/empty_impure.json
index 11f400716..d22fbf7ec 100644
--- a/src/libstore-tests/data/path-info/json-2/empty_impure.json
+++ b/src/libstore-tests/data/path-info/json-2/empty_impure.json
@@ -1,11 +1,7 @@
 {
   "ca": null,
   "deriver": null,
-  "narHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 0,
   "references": [],
   "registrationTime": null,
diff --git a/src/libstore-tests/data/path-info/json-2/empty_pure.json b/src/libstore-tests/data/path-info/json-2/empty_pure.json
index 505a42914..9d50181da 100644
--- a/src/libstore-tests/data/path-info/json-2/empty_pure.json
+++ b/src/libstore-tests/data/path-info/json-2/empty_pure.json
@@ -1,10 +1,6 @@
 {
   "ca": null,
-  "narHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 0,
   "references": [],
   "storeDir": "/nix/store",
diff --git a/src/libstore-tests/data/path-info/json-2/impure.json b/src/libstore-tests/data/path-info/json-2/impure.json
index a339d9fd2..bed67610b 100644
--- a/src/libstore-tests/data/path-info/json-2/impure.json
+++ b/src/libstore-tests/data/path-info/json-2/impure.json
@@ -1,18 +1,10 @@
 {
   "ca": {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   },
   "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-  "narHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
   "references": [
     "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
diff --git a/src/libstore-tests/data/path-info/json-2/pure.json b/src/libstore-tests/data/path-info/json-2/pure.json
index 452d83361..0350349a9 100644
--- a/src/libstore-tests/data/path-info/json-2/pure.json
+++ b/src/libstore-tests/data/path-info/json-2/pure.json
@@ -1,17 +1,9 @@
 {
   "ca": {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   },
-  "narHash": {
-    "algorithm": "sha256",
-    "format": "base16",
-    "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-  },
+  "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
   "references": [
     "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
diff --git a/src/libstore-tests/data/serve-protocol/content-address.json b/src/libstore-tests/data/serve-protocol/content-address.json
index 674c5cc68..3c63e6d9b 100644
--- a/src/libstore-tests/data/serve-protocol/content-address.json
+++ b/src/libstore-tests/data/serve-protocol/content-address.json
@@ -1,26 +1,14 @@
 [
   {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "f9773d2e5ea670f96dc1a7b0ae4fc1010e7a6371b94ffff0ce1294734ceb62ed"
-    },
+    "hash": "sha256-+Xc9Ll6mcPltwaewrk/BAQ56Y3G5T//wzhKUc0zrYu0=",
     "method": "text"
   },
   {
-    "hash": {
-      "algorithm": "sha1",
-      "format": "base16",
-      "hash": "8067a60687a7562359337862c2a9ecfc5833ab0a"
-    },
+    "hash": "sha1-gGemBoenViNZM3hiwqns/Fgzqwo=",
     "method": "flat"
   },
   {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   }
 ]
diff --git a/src/libstore-tests/data/serve-protocol/optional-content-address.json b/src/libstore-tests/data/serve-protocol/optional-content-address.json
index dc7d7d525..1c57fbf25 100644
--- a/src/libstore-tests/data/serve-protocol/optional-content-address.json
+++ b/src/libstore-tests/data/serve-protocol/optional-content-address.json
@@ -1,11 +1,7 @@
 [
   null,
   {
-    "hash": {
-      "algorithm": "sha1",
-      "format": "base16",
-      "hash": "8067a60687a7562359337862c2a9ecfc5833ab0a"
-    },
+    "hash": "sha1-gGemBoenViNZM3hiwqns/Fgzqwo=",
     "method": "flat"
   }
 ]
diff --git a/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.3.json b/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.3.json
index 8afb64da9..0f593f424 100644
--- a/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.3.json
+++ b/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.3.json
@@ -2,11 +2,7 @@
   {
     "ca": null,
     "deriver": null,
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "0000000000000000000000000000000000000000000000000000000000000000"
-    },
+    "narHash": "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
     "narSize": 34878,
     "references": [],
     "registrationTime": null,
@@ -18,11 +14,7 @@
   {
     "ca": null,
     "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "0000000000000000000000000000000000000000000000000000000000000000"
-    },
+    "narHash": "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=",
     "narSize": 34878,
     "references": [
       "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-foo.drv"
diff --git a/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.4.json b/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.4.json
index 21667e5cb..801f20400 100644
--- a/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.4.json
+++ b/src/libstore-tests/data/serve-protocol/unkeyed-valid-path-info-2.4.json
@@ -2,11 +2,7 @@
   {
     "ca": null,
     "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "references": [
       "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-foo.drv"
@@ -19,19 +15,11 @@
   },
   {
     "ca": {
-      "hash": {
-        "algorithm": "sha256",
-        "format": "base16",
-        "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-      },
+      "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
       "method": "nar"
     },
     "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "references": [
       "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
diff --git a/src/libstore-tests/data/worker-protocol/content-address.json b/src/libstore-tests/data/worker-protocol/content-address.json
index 674c5cc68..3c63e6d9b 100644
--- a/src/libstore-tests/data/worker-protocol/content-address.json
+++ b/src/libstore-tests/data/worker-protocol/content-address.json
@@ -1,26 +1,14 @@
 [
   {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "f9773d2e5ea670f96dc1a7b0ae4fc1010e7a6371b94ffff0ce1294734ceb62ed"
-    },
+    "hash": "sha256-+Xc9Ll6mcPltwaewrk/BAQ56Y3G5T//wzhKUc0zrYu0=",
     "method": "text"
   },
   {
-    "hash": {
-      "algorithm": "sha1",
-      "format": "base16",
-      "hash": "8067a60687a7562359337862c2a9ecfc5833ab0a"
-    },
+    "hash": "sha1-gGemBoenViNZM3hiwqns/Fgzqwo=",
     "method": "flat"
   },
   {
-    "hash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-    },
+    "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
     "method": "nar"
   }
 ]
diff --git a/src/libstore-tests/data/worker-protocol/optional-content-address.json b/src/libstore-tests/data/worker-protocol/optional-content-address.json
index dc7d7d525..1c57fbf25 100644
--- a/src/libstore-tests/data/worker-protocol/optional-content-address.json
+++ b/src/libstore-tests/data/worker-protocol/optional-content-address.json
@@ -1,11 +1,7 @@
 [
   null,
   {
-    "hash": {
-      "algorithm": "sha1",
-      "format": "base16",
-      "hash": "8067a60687a7562359337862c2a9ecfc5833ab0a"
-    },
+    "hash": "sha1-gGemBoenViNZM3hiwqns/Fgzqwo=",
     "method": "flat"
   }
 ]
diff --git a/src/libstore-tests/data/worker-protocol/unkeyed-valid-path-info-1.15.json b/src/libstore-tests/data/worker-protocol/unkeyed-valid-path-info-1.15.json
index a0e4fb17a..9cc53c680 100644
--- a/src/libstore-tests/data/worker-protocol/unkeyed-valid-path-info-1.15.json
+++ b/src/libstore-tests/data/worker-protocol/unkeyed-valid-path-info-1.15.json
@@ -2,11 +2,7 @@
   {
     "ca": null,
     "deriver": null,
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "references": [],
     "registrationTime": 23423,
@@ -18,11 +14,7 @@
   {
     "ca": null,
     "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "references": [
       "g1w7hyyyy1w7hy3qg1w7hy3qgqqqqy3q-foo.drv"
diff --git a/src/libstore-tests/data/worker-protocol/valid-path-info-1.15.json b/src/libstore-tests/data/worker-protocol/valid-path-info-1.15.json
index e5c1b1c40..427c286dd 100644
--- a/src/libstore-tests/data/worker-protocol/valid-path-info-1.15.json
+++ b/src/libstore-tests/data/worker-protocol/valid-path-info-1.15.json
@@ -2,11 +2,7 @@
   {
     "ca": null,
     "deriver": null,
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "path": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "references": [],
@@ -19,11 +15,7 @@
   {
     "ca": null,
     "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "path": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "references": [
diff --git a/src/libstore-tests/data/worker-protocol/valid-path-info-1.16.json b/src/libstore-tests/data/worker-protocol/valid-path-info-1.16.json
index 82b21ffba..f980d8421 100644
--- a/src/libstore-tests/data/worker-protocol/valid-path-info-1.16.json
+++ b/src/libstore-tests/data/worker-protocol/valid-path-info-1.16.json
@@ -2,11 +2,7 @@
   {
     "ca": null,
     "deriver": null,
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "path": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "references": [],
@@ -19,11 +15,7 @@
   {
     "ca": null,
     "deriver": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "path": "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "references": [
@@ -41,19 +33,11 @@
   },
   {
     "ca": {
-      "hash": {
-        "algorithm": "sha256",
-        "format": "base16",
-        "hash": "10c209fa0890fe02c85a8c663ca8e7a37cc766bc5b1b29a0cc61b266f64121d3"
-      },
+      "hash": "sha256-EMIJ+giQ/gLIWoxmPKjno3zHZrxbGymgzGGyZvZBIdM=",
       "method": "nar"
     },
     "deriver": null,
-    "narHash": {
-      "algorithm": "sha256",
-      "format": "base16",
-      "hash": "15e3c560894cbb27085cf65b5a2ecb18488c999497f4531b6907a7581ce6d527"
-    },
+    "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
     "narSize": 34878,
     "path": "n5wkd9frr45pa74if5gpz9j7mifg27fh-foo",
     "references": [
diff --git a/src/libutil-tests/data/hash/blake3-base16.json b/src/libutil-tests/data/hash/blake3-base16.json
deleted file mode 100644
index 6a7425c64..000000000
--- a/src/libutil-tests/data/hash/blake3-base16.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "algorithm": "blake3",
-  "format": "base16",
-  "hash": "9e70ee1449965fb62d049040a1ed06ec377430da6ec13173e7c4fffcd28be980"
-}
diff --git a/src/libutil-tests/data/hash/blake3.json b/src/libutil-tests/data/hash/blake3.json
new file mode 100644
index 000000000..bdb910670
--- /dev/null
+++ b/src/libutil-tests/data/hash/blake3.json
@@ -0,0 +1 @@
+"blake3-nnDuFEmWX7YtBJBAoe0G7Dd0MNpuwTFz58T//NKL6YA="
diff --git a/src/libutil-tests/data/hash/sha256-base16.json b/src/libutil-tests/data/hash/sha256-base16.json
deleted file mode 100644
index 59e10ed91..000000000
--- a/src/libutil-tests/data/hash/sha256-base16.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "algorithm": "sha256",
-  "format": "base16",
-  "hash": "f0e4c2f76c58916ec258f246851bea091d14d4247a2fc3e18694461b1816e13b"
-}
diff --git a/src/libutil-tests/data/hash/sha256-base64.json b/src/libutil-tests/data/hash/sha256-base64.json
deleted file mode 100644
index 838af80a7..000000000
--- a/src/libutil-tests/data/hash/sha256-base64.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "algorithm": "sha256",
-  "format": "base64",
-  "hash": "8OTC92xYkW7CWPJGhRvqCR0U1CR6L8PhhpRGGxgW4Ts="
-}
diff --git a/src/libutil-tests/data/hash/sha256-nix32.json b/src/libutil-tests/data/hash/sha256-nix32.json
deleted file mode 100644
index 0d6253a79..000000000
--- a/src/libutil-tests/data/hash/sha256-nix32.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-    "algorithm": "sha256",
-    "format": "nix32",
-    "hash": "0fz12qc1nillhvhw6bvs4ka18789x8dqaipjb316x4aqdkvw5r7h"
-}
diff --git a/src/libutil-tests/data/hash/sha256.json b/src/libutil-tests/data/hash/sha256.json
new file mode 100644
index 000000000..5ef584bf1
--- /dev/null
+++ b/src/libutil-tests/data/hash/sha256.json
@@ -0,0 +1 @@
+"sha256-8OTC92xYkW7CWPJGhRvqCR0U1CR6L8PhhpRGGxgW4Ts="
diff --git a/src/libutil-tests/data/hash/sha512.json b/src/libutil-tests/data/hash/sha512.json
new file mode 100644
index 000000000..5ef584bf1
--- /dev/null
+++ b/src/libutil-tests/data/hash/sha512.json
@@ -0,0 +1 @@
+"sha256-8OTC92xYkW7CWPJGhRvqCR0U1CR6L8PhhpRGGxgW4Ts="
diff --git a/src/libutil-tests/data/hash/simple.json b/src/libutil-tests/data/hash/simple.json
deleted file mode 100644
index 59e10ed91..000000000
--- a/src/libutil-tests/data/hash/simple.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "algorithm": "sha256",
-  "format": "base16",
-  "hash": "f0e4c2f76c58916ec258f246851bea091d14d4247a2fc3e18694461b1816e13b"
-}
diff --git a/src/libutil-tests/hash.cc b/src/libutil-tests/hash.cc
index d1b63c640..a6bb52d19 100644
--- a/src/libutil-tests/hash.cc
+++ b/src/libutil-tests/hash.cc
@@ -215,9 +215,6 @@ struct HashJsonTest : virtual HashTest,
                       ::testing::WithParamInterface<std::pair<std::string_view, Hash>>
 {};
 
-struct HashJsonParseFailureTest : virtual HashTest, ::testing::WithParamInterface<std::string_view>
-{};
-
 struct BLAKE3HashJsonTest : virtual HashTest,
                             BLAKE3HashTest,
                             JsonCharacterizationTest<Hash>,
@@ -236,14 +233,6 @@ TEST_P(HashJsonTest, to_json)
     writeJsonTest(name, value);
 }
 
-TEST_P(HashJsonParseFailureTest, from_json)
-{
-    auto & name = GetParam();
-    auto path = goldenMaster(Path{name} + ".json");
-    auto encoded = json::parse(readFile(path));
-    ASSERT_THROW(nlohmann::adl_serializer<Hash>::from_json(encoded), Error);
-}
-
 TEST_P(BLAKE3HashJsonTest, from_json)
 {
     auto & [name, expected] = GetParam();
@@ -256,32 +245,25 @@ TEST_P(BLAKE3HashJsonTest, to_json)
     writeJsonTest(name, expected);
 }
 
-// Round-trip tests (from_json + to_json) for base16 format only
-// (to_json always outputs base16)
 INSTANTIATE_TEST_SUITE_P(
     HashJSON,
     HashJsonTest,
     ::testing::Values(
         std::pair{
-            "simple",
+            "sha256",
             hashString(HashAlgorithm::SHA256, "asdf"),
         },
         std::pair{
-            "sha256-base16",
+            "sha512",
             hashString(HashAlgorithm::SHA256, "asdf"),
         }));
 
-// Failure tests for unsupported formats (base64, nix32, sri)
-// These verify that non-base16 formats are rejected
-INSTANTIATE_TEST_SUITE_P(
-    HashJSONParseFailure, HashJsonParseFailureTest, ::testing::Values("sha256-base64", "sha256-nix32"));
-
 INSTANTIATE_TEST_SUITE_P(BLAKE3HashJSON, BLAKE3HashJsonTest, ([] {
                              ExperimentalFeatureSettings mockXpSettings;
                              mockXpSettings.set("experimental-features", "blake3-hashes");
                              return ::testing::Values(
                                  std::pair{
-                                     "blake3-base16",
+                                     "blake3",
                                      hashString(HashAlgorithm::BLAKE3, "asdf", mockXpSettings),
                                  });
                          }()));
diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index b5d503940..ea71ffff5 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -519,27 +519,13 @@ using namespace nix;
 
 Hash adl_serializer<Hash>::from_json(const json & json, const ExperimentalFeatureSettings & xpSettings)
 {
-    auto & obj = getObject(json);
-    auto algo = parseHashAlgo(getString(valueAt(obj, "algorithm")), xpSettings);
-    auto formatStr = getString(valueAt(obj, "format"));
-    auto format = parseHashFormat(formatStr);
-
-    // Only base16 format is supported for JSON serialization
-    if (format != HashFormat::Base16) {
-        throw Error("hash format '%s' is not supported in JSON; only 'base16' is currently supported", formatStr);
-    }
-
-    auto & hashS = getString(valueAt(obj, "hash"));
-    return Hash::parseExplicitFormatUnprefixed(hashS, algo, format, xpSettings);
+    auto & s = getString(json);
+    return Hash::parseSRI(s, xpSettings);
 }
 
 void adl_serializer<Hash>::to_json(json & json, const Hash & hash)
 {
-    json = {
-        {"format", printHashFormat(HashFormat::Base16)},
-        {"algorithm", printHashAlgo(hash.algo)},
-        {"hash", hash.to_string(HashFormat::Base16, false)},
-    };
+    json = hash.to_string(HashFormat::SRI, true);
 }
 
 } // namespace nlohmann
diff --git a/tests/functional/fixed.sh b/tests/functional/fixed.sh
index 3d37f5fbb..9d769a578 100755
--- a/tests/functional/fixed.sh
+++ b/tests/functional/fixed.sh
@@ -17,11 +17,7 @@ nix-build fixed.nix -A bad --no-out-link && fail "should fail"
 nix path-info --json --json-format 2 "$path" | jq -e \
     '.info.[].ca == {
         method: "flat",
-        hash: {
-            algorithm: "md5",
-            format: "base16",
-            hash: "8ddd8be4b179a529afa5f2ffae4b9858"
-        },
+        hash: "md5-jd2L5LF5pSmvpfL/rkuYWA=="
     }'
 
 echo 'testing good...'
diff --git a/tests/functional/git-hashing/simple-common.sh b/tests/functional/git-hashing/simple-common.sh
index fa523af61..a776ec43e 100644
--- a/tests/functional/git-hashing/simple-common.sh
+++ b/tests/functional/git-hashing/simple-common.sh
@@ -47,16 +47,15 @@ try2 () {
     hashFromGit=$(git -C "$repo" rev-parse "HEAD:$hashPath")
     [[ "$hashFromGit" == "$expected" ]]
 
+    # Convert base16 hash to SRI format for comparison
+    local hashSRI
+    hashSRI=$(nix hash convert --from base16 --to sri --hash-algo "$hashAlgo" "$hashFromGit")
+
     nix path-info --json --json-format 2 "$path" | jq -e \
-        --arg algo "$hashAlgo" \
-        --arg hash "$hashFromGit" \
+        --arg hashSRI "$hashSRI" \
         '.info.[].ca == {
             method: "git",
-            hash: {
-                algorithm: $algo,
-                format: "base16",
-                hash: $hash
-            },
+            hash: $hashSRI
         }'
 }
 
diff --git a/tests/functional/impure-derivations.sh b/tests/functional/impure-derivations.sh
index 3f78036c2..b35cc6784 100755
--- a/tests/functional/impure-derivations.sh
+++ b/tests/functional/impure-derivations.sh
@@ -30,7 +30,7 @@ path1_stuff=$(echo "$json" | jq -r .[].outputs.stuff)
 [[ $(< "$path1"/n) = 0 ]]
 [[ $(< "$path1_stuff"/bla) = 0 ]]
 
-nix path-info --json --json-format 2 "$path1" | jq -e '.info.[].ca | .method == "nar" and .hash.algorithm == "sha256"'
+nix path-info --json --json-format 2 "$path1" | jq -e '.info.[].ca | .method == "nar" and (.hash | startswith("sha256-"))'
 
 path2=$(nix build -L --no-link --json --file ./impure-derivations.nix impure | jq -r .[].outputs.out)
 [[ $(< "$path2"/n) = 1 ]]
diff --git a/tests/functional/nix-profile.sh b/tests/functional/nix-profile.sh
index 8934c27fc..cf84088d7 100755
--- a/tests/functional/nix-profile.sh
+++ b/tests/functional/nix-profile.sh
@@ -166,7 +166,7 @@ printf 4.0 > "$flake1Dir"/version
 printf Utrecht > "$flake1Dir"/who
 nix profile add "$flake1Dir"
 [[ $("$TEST_HOME"/.nix-profile/bin/hello) = "Hello Utrecht" ]]
-nix path-info --json --json-format 2 "$(realpath "$TEST_HOME"/.nix-profile/bin/hello)" | jq -e '.info.[].ca | .method == "nar" and .hash.algorithm == "sha256"'
+nix path-info --json --json-format 2 "$(realpath "$TEST_HOME"/.nix-profile/bin/hello)" | jq -e '.info.[].ca | .method == "nar" and (.hash | startswith("sha256-"))'
 
 # Override the outputs.
 nix profile remove simple flake1
diff --git a/tests/functional/path-info.sh b/tests/functional/path-info.sh
index de1f45151..712b52678 100755
--- a/tests/functional/path-info.sh
+++ b/tests/functional/path-info.sh
@@ -20,16 +20,8 @@ diff --unified --color=always \
         jq --sort-keys '.info | map_values(.narHash)') \
     <(jq --sort-keys <<-EOF
         {
-          "$fooBase": {
-            "algorithm": "sha256",
-            "format": "base16",
-            "hash": "42fb4031b525feebe2f8b08e6e6a8e86f34e6a91dd036ada888e311b9cc8e690"
-          },
-          "$barBase": {
-            "algorithm": "sha256",
-            "format": "base16",
-            "hash": "f5f8581aef5fab17100b629cf35aa1d91328d5070b054068f14fa93e7fa3b614"
-          },
+          "$fooBase": "sha256-QvtAMbUl/uvi+LCObmqOhvNOapHdA2raiI4xG5zI5pA=",
+          "$barBase": "sha256-9fhYGu9fqxcQC2Kc81qh2RMo1QcLBUBo8U+pPn+jthQ=",
           "$bazBase": null
         }
 EOF
diff --git a/tests/functional/signing.sh b/tests/functional/signing.sh
index 5a3bdc81d..bfa21fcff 100755
--- a/tests/functional/signing.sh
+++ b/tests/functional/signing.sh
@@ -58,7 +58,7 @@ nix store verify -r "$outPath2" --sigs-needed 1 --trusted-public-keys "$pk1"
 # Build something content-addressed.
 outPathCA=$(IMPURE_VAR1=foo IMPURE_VAR2=bar nix-build ./fixed.nix -A good.0 --no-out-link)
 
-nix path-info --json --json-format 2 "$outPathCA" | jq -e '.info.[].ca | .method == "flat" and .hash.algorithm == "md5"'
+nix path-info --json --json-format 2 "$outPathCA" | jq -e '.info.[].ca | .method == "flat" and (.hash | startswith("md5-"))'
 
 # Content-addressed paths don't need signatures, so they verify
 # regardless of --sigs-needed.
diff --git a/tests/nixos/fetchers-substitute.nix b/tests/nixos/fetchers-substitute.nix
index 5363f8e72..bfe15c5c3 100644
--- a/tests/nixos/fetchers-substitute.nix
+++ b/tests/nixos/fetchers-substitute.nix
@@ -120,9 +120,8 @@
       # Get the NAR hash of the unpacked tarball in SRI format
       path_info_json = substituter.succeed(f"nix path-info --json-format 2 --json {tarball_store_path}").strip()
       path_info_dict = json.loads(path_info_json)["info"]
-      narHash_obj = path_info_dict[os.path.basename(tarball_store_path)]["narHash"]
-      # Convert from structured format {"algorithm": "sha256", "format": "base16", "hash": "..."} to SRI string
-      tarball_hash_sri = substituter.succeed(f"nix hash convert --to sri {narHash_obj['algorithm']}:{narHash_obj['hash']}").strip()
+      # narHash is already in SRI format
+      tarball_hash_sri = path_info_dict[os.path.basename(tarball_store_path)]["narHash"]
       print(f"Tarball NAR hash (SRI): {tarball_hash_sri}")
 
       # Also get the old format hash for fetchTarball (which uses sha256 parameter)