How to fix warning: failed to compress delta for object abc1234 in Git

GitINTERMEDIATEMEDIUM

Git fails to compress objects during pack generation, typically when pushing large repositories or running garbage collection. This memory-intensive operation can fail due to insufficient resources or corrupt objects.

What this error means

Delta compression is Git's method of storing objects efficiently by computing differences (deltas) between similar files instead of storing complete copies. When this compression fails, it usually indicates one of three problems: insufficient memory for the compression algorithm, corrupt repository objects preventing delta calculation, or system resource limits that prevent Git from completing the operation. The delta compression process is especially memory-intensive during push operations and garbage collection (`git gc`) because Git must hold multiple objects in memory simultaneously to calculate optimal deltas. The memory requirements scale with repository size and are multiplied by the number of threads configured for pack operations. This error often appears as warnings during normal operations but can escalate to fatal errors that prevent pushing to remote repositories or completing repository maintenance tasks. Understanding the underlying resource constraints is key to resolving these issues.

How to fix "warning: failed to compress delta for object abc1234"

1Check repository integrity

Before adjusting memory settings, verify your repository isn't corrupted:

bash

git fsck --full --no-dangling

If this reports errors, you may need to repair the repository before proceeding. A clean fsck output indicates the issue is resource-related rather than corruption.

2Reduce memory usage with conservative pack settings

Configure Git to use less memory during delta compression:

bash

git config --global pack.windowMemory "256m"
git config --global pack.packSizeLimit "256m"
git config --global pack.threads 1
git config --global pack.deltaCacheSize "128m"

These settings limit memory consumption by:
- pack.windowMemory: Caps memory per thread to 256MB
- pack.threads: Reduces to single-threaded operation
- pack.deltaCacheSize: Limits delta cache to 128MB

For local repositories only, use git config without --global.

3Run garbage collection with memory limits

Manually repack the repository with controlled memory usage:

bash

git gc --aggressive --prune=now

If this still fails, try a more conservative repack:

bash

git repack -a -d -f --depth=50 --window=50

The lower --depth and --window values reduce memory requirements at the cost of slightly less optimal compression.

4Increase HTTP buffer for large pushes

If the error occurs during push operations, increase the post buffer:

bash

git config --global http.postBuffer 524288000

This sets the buffer to 500MB, helping with large pack transfers over HTTP. Adjust the value based on your typical commit sizes.

5Push in smaller batches

For repositories with many unpushed commits, push branches individually:

bash

# Push current branch only
git push origin HEAD

# Or push specific branches
git push origin feature-branch-1
git push origin feature-branch-2

Avoid git push --all when experiencing compression issues.

6Disable delta compression for problematic files

If specific file types cause compression issues, disable delta compression in .gitattributes:

bash

# Add to .gitattributes in repository root
*.zip -delta
*.jar -delta
*.png -delta
*.jpg -delta
*.mp4 -delta

This prevents Git from attempting delta compression on binary files that don't compress well. Commit this file and run git gc again.

How to fix warning: failed to compress delta for object abc1234 in Git

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How to fix "warning: failed to compress delta for object abc1234"

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