Git Branch Name Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching git branch name, ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# Git Branch Name
# ReDoS-safe | RegexVault — Dev & Systems > Git

import re

git_branch_name_pattern = re.compile(r'^(?!HEAD$|FETCH_HEAD$|ORIG_HEAD$|MERGE_HEAD$)(?!.*\.\.)(?!.*\s)[a-zA-Z0-9][a-zA-Z0-9._\-/]{0,249}$')

def validate_git_branch_name(value: str) -> bool:
    return bool(git_branch_name_pattern.fullmatch(value))

# Example
print(validate_git_branch_name("main"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Git category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Git branch names cannot contain .., whitespace, control characters, or reserved names (HEAD, FETCH_HEAD). Lookaheads enforce these constraints. Go's RE2 does not support lookaheads — validate separately.