diff --git a/Cargo.lock b/Cargo.lock
index 32b243e84..0fadeb370 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1631,12 +1631,6 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fbf6a919d6cf397374f7dfeeea91d974c7c0a7221d0d0f4f20d859d329e53fcc"
 
-[[package]]
-name = "hex"
-version = "0.4.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
-
 [[package]]
 name = "home"
 version = "0.5.9"
@@ -1839,6 +1833,7 @@ dependencies = [
  "dirs",
  "dunce",
  "esl01-renderdag",
+ "faster-hex",
  "futures 0.3.30",
  "git2",
  "gix",
@@ -1897,7 +1892,6 @@ dependencies = [
  "gix",
  "gix-filter",
  "glob",
- "hex",
  "ignore",
  "indexmap",
  "indoc",
@@ -3109,9 +3103,9 @@ version = "0.22.0"
 dependencies = [
  "async-trait",
  "config",
+ "faster-hex",
  "futures 0.3.30",
  "git2",
- "hex",
  "itertools 0.13.0",
  "jj-lib",
  "pollster",
diff --git a/Cargo.toml b/Cargo.toml
index 09a4d1cd2..197078fde 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -66,7 +66,7 @@ gix = { version = "0.66.0", default-features = false, features = [
 ] }
 gix-filter = "0.13.0"
 glob = "0.3.1"
-hex = "0.4.3"
+faster-hex = { version = "0.9.0", default-features = false, features = ["std"]}
 ignore = "0.4.23"
 indexmap = "2.6.0"
 indoc = "2.0.4"
diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index ef261d178..ecafc4e0b 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -64,6 +64,7 @@ esl01-renderdag = { workspace = true }
 futures = { workspace = true }
 git2 = { workspace = true }
 gix = { workspace = true }
+faster-hex = { workspace = true }
 indexmap = { workspace = true }
 indoc = { workspace = true }
 itertools = { workspace = true }
diff --git a/cli/src/cli_util.rs b/cli/src/cli_util.rs
index 273acc4fa..7a3c93da1 100644
--- a/cli/src/cli_util.rs
+++ b/cli/src/cli_util.rs
@@ -64,7 +64,6 @@ use jj_lib::git;
 use jj_lib::git_backend::GitBackend;
 use jj_lib::gitignore::GitIgnoreError;
 use jj_lib::gitignore::GitIgnoreFile;
-use jj_lib::hex_util::to_reverse_hex;
 use jj_lib::id_prefix::IdPrefixContext;
 use jj_lib::matchers::Matcher;
 use jj_lib::merge::MergedTreeValue;
@@ -2650,17 +2649,21 @@ pub fn edit_temp_file(
 }
 
 pub fn short_commit_hash(commit_id: &CommitId) -> String {
-    commit_id.hex()[0..12].to_string()
+    let mut hash = commit_id.hex();
+    hash.truncate(12);
+    hash
 }
 
 pub fn short_change_hash(change_id: &ChangeId) -> String {
-    // TODO: We could avoid the unwrap() and make this more efficient by converting
-    // straight from binary.
-    to_reverse_hex(&change_id.hex()[0..12]).unwrap()
+    let mut hash = change_id.reverse_hex();
+    hash.truncate(12);
+    hash
 }
 
 pub fn short_operation_hash(operation_id: &OperationId) -> String {
-    operation_id.hex()[0..12].to_string()
+    let mut hash = operation_id.hex();
+    hash.truncate(12);
+    hash
 }
 
 /// Wrapper around a `DiffEditor` to conditionally start interactive session.
diff --git a/cli/src/commands/debug/tree.rs b/cli/src/commands/debug/tree.rs
index 7c40d33b5..38e2647e0 100644
--- a/cli/src/commands/debug/tree.rs
+++ b/cli/src/commands/debug/tree.rs
@@ -47,7 +47,7 @@ pub fn cmd_debug_tree(
     let workspace_command = command.workspace_helper(ui)?;
     let tree = if let Some(tree_id_hex) = &args.id {
         let tree_id =
-            TreeId::try_from_hex(tree_id_hex).map_err(|_| user_error("Invalid tree id"))?;
+            TreeId::try_from_hex(tree_id_hex).ok_or_else(|| user_error("Invalid tree id"))?;
         let dir = if let Some(dir_str) = &args.dir {
             workspace_command.parse_file_path(dir_str)?
         } else {
diff --git a/cli/src/commit_templater.rs b/cli/src/commit_templater.rs
index d52dbcd0c..95c531df7 100644
--- a/cli/src/commit_templater.rs
+++ b/cli/src/commit_templater.rs
@@ -31,7 +31,6 @@ use jj_lib::fileset;
 use jj_lib::fileset::FilesetDiagnostics;
 use jj_lib::fileset::FilesetExpression;
 use jj_lib::git;
-use jj_lib::hex_util::to_reverse_hex;
 use jj_lib::id_prefix::IdPrefixContext;
 use jj_lib::matchers::Matcher;
 use jj_lib::merged_tree::MergedTree;
@@ -1248,11 +1247,7 @@ impl CommitOrChangeId {
     pub fn hex(&self) -> String {
         match self {
             CommitOrChangeId::Commit(id) => id.hex(),
-            CommitOrChangeId::Change(id) => {
-                // TODO: We can avoid the unwrap() and make this more efficient by converting
-                // straight from bytes.
-                to_reverse_hex(&id.hex()).unwrap()
-            }
+            CommitOrChangeId::Change(id) => id.reverse_hex(),
         }
     }
 
diff --git a/lib/Cargo.toml b/lib/Cargo.toml
index e45e45f88..4834c40e2 100644
--- a/lib/Cargo.toml
+++ b/lib/Cargo.toml
@@ -48,7 +48,6 @@ git2 = { workspace = true, optional = true }
 gix = { workspace = true, optional = true }
 gix-filter = { workspace = true, optional = true }
 glob = { workspace = true }
-hex = { workspace = true }
 ignore = { workspace = true }
 indexmap = { workspace = true }
 itertools = { workspace = true }
diff --git a/lib/src/backend.rs b/lib/src/backend.rs
index 32b04ae26..a5786e5d5 100644
--- a/lib/src/backend.rs
+++ b/lib/src/backend.rs
@@ -25,6 +25,7 @@ use futures::stream::BoxStream;
 use thiserror::Error;
 
 use crate::content_hash::ContentHash;
+use crate::hex_util;
 use crate::index::Index;
 use crate::merge::Merge;
 use crate::object_id::id_type;
@@ -50,6 +51,12 @@ id_type!(pub FileId);
 id_type!(pub SymlinkId);
 id_type!(pub ConflictId);
 
+impl ChangeId {
+    pub fn reverse_hex(&self) -> String {
+        hex_util::encode_hex_string_reverse(&self.0)
+    }
+}
+
 #[derive(ContentHash, Debug, PartialEq, Eq, Clone, Copy, PartialOrd, Ord)]
 pub struct MillisSinceEpoch(pub i64);
 
diff --git a/lib/src/content_hash.rs b/lib/src/content_hash.rs
index e3918589a..bbe923567 100644
--- a/lib/src/content_hash.rs
+++ b/lib/src/content_hash.rs
@@ -151,6 +151,7 @@ mod tests {
     use std::collections::HashMap;
 
     use super::*;
+    use crate::hex_util;
 
     #[test]
     fn test_string_sanity() {
@@ -215,7 +216,7 @@ mod tests {
             x: Vec<Option<i32>>,
             y: i64,
         }
-        let foo_hash = hex::encode(hash(&Foo {
+        let foo_hash = hex_util::encode_hex_string(&hash(&Foo {
             x: vec![None, Some(42)],
             y: 17,
         }));
@@ -231,7 +232,7 @@ mod tests {
             y: Y,
         }
         assert_eq!(
-            hex::encode(hash(&GenericFoo {
+            hex_util::encode_hex_string(&hash(&GenericFoo {
                 x: vec![None, Some(42)],
                 y: 17i64
             })),
diff --git a/lib/src/default_index/mutable.rs b/lib/src/default_index/mutable.rs
index 353550dbe..c6d2998d9 100644
--- a/lib/src/default_index/mutable.rs
+++ b/lib/src/default_index/mutable.rs
@@ -48,6 +48,7 @@ use crate::backend::ChangeId;
 use crate::backend::CommitId;
 use crate::commit::Commit;
 use crate::file_util::persist_content_addressed_temp_file;
+use crate::hex_util;
 use crate::index::AllHeadsForGcUnsupported;
 use crate::index::ChangeIdIndex;
 use crate::index::Index;
@@ -359,7 +360,7 @@ impl MutableIndexSegment {
         self.serialize_local_entries(&mut buf);
         let mut hasher = Blake2b512::new();
         hasher.update(&buf);
-        let index_file_id_hex = hex::encode(hasher.finalize());
+        let index_file_id_hex = hex_util::encode_hex_string(&hasher.finalize());
         let index_file_path = dir.join(&index_file_id_hex);
 
         let mut temp_file = NamedTempFile::new_in(dir)?;
diff --git a/lib/src/git_backend.rs b/lib/src/git_backend.rs
index 7d2b267e9..84ba228f2 100644
--- a/lib/src/git_backend.rs
+++ b/lib/src/git_backend.rs
@@ -500,7 +500,7 @@ fn root_tree_from_header(git_commit: &CommitRef) -> Result<Option<MergedTreeId>,
         if *key == JJ_TREES_COMMIT_HEADER {
             let mut tree_ids = SmallVec::new();
             for hex in str::from_utf8(value.as_ref()).or(Err(()))?.split(' ') {
-                let tree_id = TreeId::try_from_hex(hex).or(Err(()))?;
+                let tree_id = TreeId::try_from_hex(hex).ok_or(())?;
                 if tree_id.as_bytes().len() != HASH_LENGTH {
                     return Err(());
                 }
@@ -1505,19 +1505,19 @@ fn tree_value_from_json(json: &serde_json::Value) -> TreeValue {
 }
 
 fn bytes_vec_from_json(value: &serde_json::Value) -> Vec<u8> {
-    hex::decode(value.as_str().unwrap()).unwrap()
+    crate::hex_util::decode_hex_string(value.as_str().unwrap()).unwrap()
 }
 
 #[cfg(test)]
 mod tests {
     use assert_matches::assert_matches;
     use git2::Oid;
-    use hex::ToHex;
     use pollster::FutureExt;
     use test_case::test_case;
 
     use super::*;
     use crate::content_hash::blake2b_hash;
+    use crate::hex_util;
 
     #[test_case(false; "legacy tree format")]
     #[test_case(true; "tree-level conflict format")]
@@ -2133,7 +2133,7 @@ mod tests {
         };
 
         let mut signer = |data: &_| {
-            let hash: String = blake2b_hash(data).encode_hex();
+            let hash: String = hex_util::encode_hex_string(&blake2b_hash(data));
             Ok(format!("test sig\n\n\nhash={hash}").into_bytes())
         };
 
diff --git a/lib/src/hex_util.rs b/lib/src/hex_util.rs
index 48517b38f..a7edeb5df 100644
--- a/lib/src/hex_util.rs
+++ b/lib/src/hex_util.rs
@@ -14,14 +14,20 @@
 
 #![allow(missing_docs)]
 
+use std::iter;
+
+/// Converts a hexadecimal ASCII character to a 0-based index.
+fn hex_to_relative(b: u8) -> Option<u8> {
+    match b {
+        b'0'..=b'9' => Some(b - b'0'),
+        b'A'..=b'F' => Some(b - b'A' + 10),
+        b'a'..=b'f' => Some(b - b'a' + 10),
+        _ => None,
+    }
+}
+
 fn to_reverse_hex_digit(b: u8) -> Option<u8> {
-    let value = match b {
-        b'0'..=b'9' => b - b'0',
-        b'A'..=b'F' => b - b'A' + 10,
-        b'a'..=b'f' => b - b'a' + 10,
-        _ => return None,
-    };
-    Some(b'z' - value)
+    Some(b'z' - hex_to_relative(b)?)
 }
 
 fn to_forward_hex_digit(b: u8) -> Option<u8> {
@@ -37,6 +43,10 @@ fn to_forward_hex_digit(b: u8) -> Option<u8> {
     }
 }
 
+/// Transforms a reverse hex into a forward hex.
+///
+/// If the reverse hex string contains non reverse hex characters the function
+/// will return None.
 pub fn to_forward_hex(reverse_hex: &str) -> Option<String> {
     reverse_hex
         .bytes()
@@ -44,6 +54,10 @@ pub fn to_forward_hex(reverse_hex: &str) -> Option<String> {
         .collect()
 }
 
+/// Transforms a forward hex into a reverse hex.
+///
+/// If the forward hex string contains non forward hex characters the function
+/// will return None.
 pub fn to_reverse_hex(forward_hex: &str) -> Option<String> {
     forward_hex
         .bytes()
@@ -51,6 +65,19 @@ pub fn to_reverse_hex(forward_hex: &str) -> Option<String> {
         .collect()
 }
 
+pub fn decode_hex_string(src: &str) -> Option<Vec<u8>> {
+    if src.len() % 2 != 0 {
+        return None;
+    }
+    let mut dst = vec![0; src.len() / 2];
+    for (slot, bytes) in iter::zip(&mut dst, src.as_bytes().chunks_exact(2)) {
+        let a = hex_to_relative(bytes[0])? << 4;
+        let b = hex_to_relative(bytes[1])?;
+        *slot = a | b;
+    }
+    Some(dst)
+}
+
 /// Calculates common prefix length of two byte sequences. The length
 /// to be returned is a number of hexadecimal digits.
 pub fn common_hex_len(bytes_a: &[u8], bytes_b: &[u8]) -> usize {
@@ -64,10 +91,81 @@ pub fn common_hex_len(bytes_a: &[u8], bytes_b: &[u8]) -> usize {
         .unwrap_or_else(|| bytes_a.len().min(bytes_b.len()) * 2)
 }
 
+pub fn encode_hex_string_reverse(src: &[u8]) -> String {
+    let mut dst = vec![0; src.len() * 2];
+    for (&src, dst) in src.iter().zip(dst.chunks_exact_mut(2)) {
+        dst[0] = hex_lower_reverse((src >> 4) & 0xf);
+        dst[1] = hex_lower_reverse(src & 0xf);
+    }
+    String::from_utf8(dst).expect("hex_lower_reverse emits ascii character bytes")
+}
+
+fn hex_lower_reverse(byte: u8) -> u8 {
+    static TABLE: &[u8] = b"zyxwvutsrqponmlk";
+    TABLE[byte as usize]
+}
+
+pub fn encode_hex_string(src: &[u8]) -> String {
+    let mut dst = vec![0; src.len() * 2];
+    for (&src, dst) in src.iter().zip(dst.chunks_exact_mut(2)) {
+        dst[0] = hex_lower((src >> 4) & 0xf);
+        dst[1] = hex_lower(src & 0xf);
+    }
+    String::from_utf8(dst).expect("hex_lower emits ascii character bytes")
+}
+
+fn hex_lower(byte: u8) -> u8 {
+    static TABLE: &[u8] = b"0123456789abcdef";
+    TABLE[byte as usize]
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_common_hex_len() {
+        assert_eq!(common_hex_len(b"", b""), 0);
+        assert_eq!(common_hex_len(b"abc", b"abc"), 6);
+
+        assert_eq!(common_hex_len(b"aaa", b"bbb"), 1);
+        assert_eq!(common_hex_len(b"aab", b"aac"), 5);
+    }
+
+    #[test]
+    fn test_encode_hex_string() {
+        assert_eq!(&encode_hex_string(b""), "");
+        assert_eq!(&encode_hex_string(b"012"), "303132");
+        assert_eq!(&encode_hex_string(b"0123"), "30313233");
+        assert_eq!(&encode_hex_string(b"abdz"), "6162647a");
+    }
+
+    #[test]
+    fn test_encode_hex_string_reverse() {
+        assert_eq!(&encode_hex_string_reverse(b""), "");
+        assert_eq!(&encode_hex_string_reverse(b"012"), "wzwywx");
+        assert_eq!(&encode_hex_string_reverse(b"0123"), "wzwywxww");
+        assert_eq!(&encode_hex_string_reverse(b"abdz"), "tytxtvsp");
+    }
+
+    #[test]
+    fn test_decode_hex_string() {
+        // Empty string
+        assert_eq!(decode_hex_string(""), Some(vec![]));
+
+        // Odd number of digits
+        assert_eq!(decode_hex_string("0"), None);
+
+        // Invalid digit
+        assert_eq!(decode_hex_string("g0"), None);
+        assert_eq!(decode_hex_string("0g"), None);
+
+        assert_eq!(
+            decode_hex_string("0123456789abcdefABCDEF"),
+            Some(b"\x01\x23\x45\x67\x89\xab\xcd\xef\xAB\xCD\xEF".to_vec())
+        );
+    }
+
     #[test]
     fn test_reverse_hex() {
         // Empty string
diff --git a/lib/src/object_id.rs b/lib/src/object_id.rs
index 061b68bf1..90450272f 100644
--- a/lib/src/object_id.rs
+++ b/lib/src/object_id.rs
@@ -66,8 +66,8 @@ macro_rules! impl_id_type {
             }
 
             /// Parses the given hex string into an ObjectId.
-            pub fn try_from_hex(hex: &str) -> Result<Self, hex::FromHexError> {
-                hex::decode(hex).map(Self)
+            pub fn try_from_hex(hex: &str) -> Option<Self> {
+                $crate::hex_util::decode_hex_string(hex).map(Self)
             }
         }
 
@@ -95,7 +95,7 @@ macro_rules! impl_id_type {
             }
 
             fn hex(&self) -> String {
-                hex::encode(&self.0)
+                $crate::hex_util::encode_hex_string(&self.0)
             }
         }
     };
@@ -104,6 +104,9 @@ macro_rules! impl_id_type {
 pub(crate) use id_type;
 pub(crate) use impl_id_type;
 
+use crate::hex_util::decode_hex_string;
+use crate::hex_util::{self};
+
 /// An identifier prefix (typically from a type implementing the [`ObjectId`]
 /// trait) with facilities for converting between bytes and a hex string.
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -120,9 +123,9 @@ impl HexPrefix {
     pub fn new(prefix: &str) -> Option<HexPrefix> {
         let has_odd_byte = prefix.len() & 1 != 0;
         let min_prefix_bytes = if has_odd_byte {
-            hex::decode(prefix.to_owned() + "0").ok()?
+            decode_hex_string(&format!("{prefix}0"))?
         } else {
-            hex::decode(prefix).ok()?
+            decode_hex_string(prefix)?
         };
         Some(HexPrefix {
             min_prefix_bytes,
@@ -138,7 +141,7 @@ impl HexPrefix {
     }
 
     pub fn hex(&self) -> String {
-        let mut hex_string = hex::encode(&self.min_prefix_bytes);
+        let mut hex_string = hex_util::encode_hex_string(&self.min_prefix_bytes);
         if self.has_odd_byte {
             hex_string.pop().unwrap();
         }
diff --git a/lib/src/simple_op_heads_store.rs b/lib/src/simple_op_heads_store.rs
index e4b05a1c1..d8e59b2f9 100644
--- a/lib/src/simple_op_heads_store.rs
+++ b/lib/src/simple_op_heads_store.rs
@@ -21,6 +21,7 @@ use std::fs;
 use std::path::Path;
 use std::path::PathBuf;
 
+use crate::hex_util::decode_hex_string;
 use crate::lock::FileLock;
 use crate::object_id::ObjectId;
 use crate::op_heads_store::OpHeadsStore;
@@ -96,7 +97,7 @@ impl OpHeadsStore for SimpleOpHeadsStore {
         for op_head_entry in std::fs::read_dir(&self.dir).unwrap() {
             let op_head_file_name = op_head_entry.unwrap().file_name();
             let op_head_file_name = op_head_file_name.to_str().unwrap();
-            if let Ok(op_head) = hex::decode(op_head_file_name) {
+            if let Some(op_head) = decode_hex_string(op_head_file_name) {
                 op_heads.push(OperationId::new(op_head));
             }
         }
diff --git a/lib/src/simple_op_store.rs b/lib/src/simple_op_store.rs
index 1cadb9ce9..c76e49dfd 100644
--- a/lib/src/simple_op_store.rs
+++ b/lib/src/simple_op_store.rs
@@ -228,7 +228,7 @@ impl OpStore for SimpleOpStore {
                 if !name.starts_with(&hex_prefix) {
                     continue;
                 }
-                let Ok(id) = OperationId::try_from_hex(&name) else {
+                let Some(id) = OperationId::try_from_hex(&name) else {
                     continue; // Skip invalid hex
                 };
                 if matched.is_some() {
@@ -251,11 +251,11 @@ impl OpStore for SimpleOpStore {
     fn gc(&self, head_ids: &[OperationId], keep_newer: SystemTime) -> OpStoreResult<()> {
         let to_op_id = |entry: &fs::DirEntry| -> Option<OperationId> {
             let name = entry.file_name().into_string().ok()?;
-            OperationId::try_from_hex(&name).ok()
+            OperationId::try_from_hex(&name)
         };
         let to_view_id = |entry: &fs::DirEntry| -> Option<ViewId> {
             let name = entry.file_name().into_string().ok()?;
-            ViewId::try_from_hex(&name).ok()
+            ViewId::try_from_hex(&name)
         };
         let remove_file_if_not_new = |entry: &fs::DirEntry| -> Result<(), PathError> {
             let path = entry.path();
diff --git a/lib/src/stacked_table.rs b/lib/src/stacked_table.rs
index d88e05366..f2a7ee71e 100644
--- a/lib/src/stacked_table.rs
+++ b/lib/src/stacked_table.rs
@@ -37,6 +37,7 @@ use tempfile::NamedTempFile;
 use thiserror::Error;
 
 use crate::file_util::persist_content_addressed_temp_file;
+use crate::hex_util;
 use crate::lock::FileLock;
 
 pub trait TableSegment {
@@ -333,7 +334,7 @@ impl MutableTable {
         let buf = self.maybe_squash_with_ancestors().serialize();
         let mut hasher = Blake2b512::new();
         hasher.update(&buf);
-        let file_id_hex = hex::encode(hasher.finalize());
+        let file_id_hex = hex_util::encode_hex_string(&hasher.finalize());
         let file_path = store.dir.join(&file_id_hex);
 
         let mut temp_file = NamedTempFile::new_in(&store.dir)?;
diff --git a/lib/tests/test_git.rs b/lib/tests/test_git.rs
index d9106f994..9ff03c44e 100644
--- a/lib/tests/test_git.rs
+++ b/lib/tests/test_git.rs
@@ -44,6 +44,7 @@ use jj_lib::git::GitRefUpdate;
 use jj_lib::git::RefName;
 use jj_lib::git::SubmoduleConfig;
 use jj_lib::git_backend::GitBackend;
+use jj_lib::hex_util;
 use jj_lib::object_id::ObjectId;
 use jj_lib::op_store::BookmarkTarget;
 use jj_lib::op_store::RefTarget;
@@ -1381,8 +1382,8 @@ fn test_import_refs_missing_git_commit() {
 
     let commit1 = empty_git_commit(&git_repo, "refs/heads/main", &[]);
     let commit2 = empty_git_commit(&git_repo, "refs/heads/main", &[&commit1]);
-    let shard = hex::encode(&commit1.id().as_bytes()[..1]);
-    let object_basename = hex::encode(&commit1.id().as_bytes()[1..]);
+    let shard = hex_util::encode_hex_string(&commit1.id().as_bytes()[..1]);
+    let object_basename = hex_util::encode_hex_string(&commit1.id().as_bytes()[1..]);
     let object_store_path = git_repo.path().join("objects");
     let object_file = object_store_path.join(&shard).join(object_basename);
     let backup_object_file = object_store_path.join(&shard).join("backup");
diff --git a/lib/tests/test_revset.rs b/lib/tests/test_revset.rs
index 3034c1293..6b71f0375 100644
--- a/lib/tests/test_revset.rs
+++ b/lib/tests/test_revset.rs
@@ -275,22 +275,22 @@ fn test_resolve_symbol_change_id(readonly: bool) {
 
     // Test the test setup
     assert_eq!(
-        hex::encode(git_commit_ids[0]),
+        &format!("{}", git_commit_ids[0]),
         // "04e12a5467bba790efb88a9870894ec208b16bf1" reversed
         "8fd68d104372910e19511df709e5dde62a548720"
     );
     assert_eq!(
-        hex::encode(git_commit_ids[1]),
+        &format!("{}", git_commit_ids[1]),
         // "040b3ba3a51d8edbc4c5855cbd09de71d4c29cca" reversed
         "5339432b8e7b90bd3aa1a323db71b8a5c5dcd020"
     );
     assert_eq!(
-        hex::encode(git_commit_ids[2]),
+        &format!("{}", git_commit_ids[2]),
         // "04e1c7082e4e34f3f371d8a1a46770b861b9b547" reversed
         "e2ad9d861d0ee625851b8ecfcf2c727410e38720"
     );
     assert_eq!(
-        hex::encode(git_commit_ids[3]),
+        &format!("{}", git_commit_ids[3]),
         // "911d7e52fd5ba04b8f289e14c3d30b52d38c0020" reversed
         "040031cb4ad0cbc3287914f1d205dabf4a7eb889"
     );
diff --git a/lib/testutils/Cargo.toml b/lib/testutils/Cargo.toml
index 62b0ed866..2f065ae23 100644
--- a/lib/testutils/Cargo.toml
+++ b/lib/testutils/Cargo.toml
@@ -19,7 +19,7 @@ async-trait = { workspace = true }
 config = { workspace = true }
 futures = { workspace = true }
 git2 = { workspace = true }
-hex = { workspace = true }
+faster-hex = { workspace = true }
 itertools = { workspace = true }
 jj-lib = { workspace = true, features = ["testing"] }
 pollster = { workspace = true }
diff --git a/lib/testutils/src/test_signing_backend.rs b/lib/testutils/src/test_signing_backend.rs
index 8d1d3369b..d687844c4 100644
--- a/lib/testutils/src/test_signing_backend.rs
+++ b/lib/testutils/src/test_signing_backend.rs
@@ -1,5 +1,5 @@
-use hex::ToHex;
 use jj_lib::content_hash::blake2b_hash;
+use jj_lib::hex_util;
 use jj_lib::signing::SigStatus;
 use jj_lib::signing::SignError;
 use jj_lib::signing::SignResult;
@@ -26,7 +26,7 @@ impl SigningBackend for TestSigningBackend {
         body.extend_from_slice(key.as_bytes());
         body.extend_from_slice(data);
 
-        let hash: String = blake2b_hash(&body).encode_hex();
+        let hash: String = hex_util::encode_hex_string(&blake2b_hash(&body));
 
         Ok(format!("{PREFIX}{key}\n{hash}").into_bytes())
     }