GitHub Actions environment file too large

The runner imposes a size cap on the environment files. Writing a large blob (a whole file, a big JSON payload) to $GITHUB_ENV or $GITHUB_OUTPUT trips the limit and fails the step.

What this error means

A step writing to an environment file fails with a too-large error.

github-actions

Error: The environment file is too large.
Writing this much data to $GITHUB_ENV / $GITHUB_OUTPUT exceeds the allowed size.

Common causes

Large payload into env/output

A step appends a whole file or large variable to $GITHUB_ENV or $GITHUB_OUTPUT.

How to fix it

Pass large data via artifacts or files

Store large data on disk and reference the path, or upload it as an artifact.
Only pass small identifiers/paths through environment files.

.github/workflows/ci.yml

- run: |
    echo "result_path=${RUNNER_TEMP}/result.json" >> "${GITHUB_OUTPUT}"
    cp big.json "${RUNNER_TEMP}/result.json"

How to prevent it

Keep env/output values small (ids, flags, short paths).
Use artifacts or the filesystem for large blobs.

Related guides

GitHub Actions "step output exceeds max size"Fix the GitHub Actions error where a step writes an output to GITHUB_OUTPUT that exceeds the allowed size. GitHub Actions Job Outputs Truncated or Dropped at Size LimitFix GitHub Actions job outputs that come through truncated or empty - job and step outputs have a size cap, s… GitHub Actions "secret too large (64KB limit)"Fix the GitHub Actions error where a secret value exceeds the 64KB size limit.