How to fix fatal: the remote end hung up unexpectedly in Git

The most common fix is to increase Git's HTTP buffer, which defaults to only 1 MB:

# Set buffer to 500 MB (recommended starting point)
git config --global http.postBuffer 524288000

For very large repositories, you may need even more:

# Set buffer to 1 GB
git config --global http.postBuffer 1048576000

To set this only for the current repository (not globally):

git config http.postBuffer 524288000

After changing this setting, retry your git operation.

If you're on a slow or unstable network, adjust timeout settings:

# Disable low speed limit (prevents timeout on slow connections)
git config --global http.lowSpeedLimit 0
git config --global http.lowSpeedTime 999999

These settings tell Git not to abort the connection even if the transfer speed drops very low.

Compression adds CPU overhead and can cause issues with very large transfers:

# Disable compression
git config --global core.compression 0

# Optionally limit pack window size
git config --global pack.window 1

This trades bandwidth for reliability - useful when the issue is timeout-related rather than bandwidth-related.

SSH connections are often more reliable for large transfers and avoid HTTP-related buffer issues:

Check your current remote URL:

git remote -v

Change from HTTPS to SSH:

# GitHub
git remote set-url origin [email protected]:username/repository.git

# GitLab
git remote set-url origin [email protected]:username/repository.git

# Bitbucket
git remote set-url origin [email protected]:username/repository.git

Ensure your SSH key is set up:

# Check if you have an SSH key
ls -la ~/.ssh/

# Test SSH connection to GitHub
ssh -T [email protected]

# Test SSH connection to GitLab
ssh -T [email protected]

If you don't have an SSH key configured, see your hosting provider's documentation for SSH key setup.

If you have many commits or large changes, push them incrementally:

# Push commits one at a time
git log --oneline origin/main..HEAD | tail -1
# Get the oldest commit hash, then:
git push origin <commit-hash>:main
# Repeat for remaining commits

Or use a script to push incrementally:

#!/bin/bash
# Push commits in batches of 10
for commit in $(git rev-list --reverse origin/main..HEAD | awk 'NR % 10 == 0'); do
  git push origin $commit:main
done
git push origin HEAD:main

This approach is especially useful when you have a backlog of many commits to push.

When cloning large repositories, use a shallow clone to reduce data transfer:

# Clone only the last 1 commit
git clone --depth 1 https://github.com/username/repository.git

# Clone only the last 10 commits
git clone --depth 10 https://github.com/username/repository.git

# Later, if you need full history:
git fetch --unshallow

For very large repositories, you can also clone only a specific branch:

git clone --depth 1 --branch main --single-branch https://github.com/username/repository.git

Large files are a common cause of this error. Find them before pushing:

# Find large files in your working directory
find . -type f -size +50M -not -path './.git/*'

# Find large files in git history
git rev-list --objects --all | \
  git cat-file --batch-check='%(objecttype) %(objectname) %(objectsize) %(rest)' | \
  awk '/^blob/ {print substr($0,6)}' | \
  sort -rnk2 | \
  head -20

If you find large files that shouldn't be in the repository:
- Add them to .gitignore
- Consider using Git LFS (Large File Storage) for files that need versioning
- Remove them from history using git filter-repo if already committed

Get verbose output to understand exactly where the failure occurs:

On Linux/macOS:

export GIT_TRACE_PACKET=1
export GIT_TRACE=1
export GIT_CURL_VERBOSE=1
git push

On Windows (PowerShell):

$env:GIT_TRACE_PACKET=1
$env:GIT_TRACE=1
$env:GIT_CURL_VERBOSE=1
git push

This will show detailed information about the HTTP requests and responses, helping identify whether the issue is:
- Connection timeout
- Server rejection (look for HTTP 413 or 408 status codes)
- SSL/TLS issues
- Authentication problems

Corporate networks often have proxies or firewalls that interfere with large transfers:

Check current proxy settings:

git config --global --get http.proxy
git config --global --get https.proxy

If you need to use a proxy:

git config --global http.proxy http://proxy.example.com:8080
git config --global https.proxy http://proxy.example.com:8080

If proxy is causing issues, try without it (if network allows):

git config --global --unset http.proxy
git config --global --unset https.proxy

For VPN issues, try:
- Temporarily disconnecting from VPN
- Using SSH instead of HTTPS
- Contacting your IT department about git traffic whitelisting

If other solutions don't work, the issue may be network-specific:

- Switch from WiFi to mobile data (or vice versa) to test
- Try a different WiFi network if available
- Restart your router to get a fresh connection
- Reinstall network drivers on Windows if issue persists across networks

If the operation works on a different network, the issue is likely:
- ISP-level traffic shaping
- Network equipment limitations
- Firewall or security software on the original network

In CI/CD environments, this may indicate network issues with the build runner.