Docker build context inspector

What it does

Explain missing or excluded Docker COPY sources using a local folder, Dockerfile and ignore rules.

How to use it

1. Select a local context folder or ZIP, choose the Dockerfile and context path, then inspect supported COPY sources.
2. Follow file locations and the governing ignore rule. Dockerfile-specific ignore files take precedence when supplied.
3. The report does not run Docker, execute a build or fetch remote sources. Unsupported expressions remain explicit gaps.

Example

COPY app/config.json is excluded by an ignore rule, while COPY missing.txt has no matching path in the selected context.

Methodology

A bounded local inventory is matched against literal COPY sources using case-sensitive POSIX paths, Go-style source globs and ordered Docker ignore rules. A supplied Dockerfile-specific ignore file replaces the context-root ignore file. Findings retain Dockerfile and decisive ignore-rule locations.

Limitations

2,000 folder files; 5 MB ZIP / 100 entries / 10 MB expanded; 256 KB per config and 10 MB combined text. Limits use decimal bytes. At most 500 ignore rules, 100 COPY sources, 2 million report characters and 30 seconds. Empty directories and symlink targets are not represented. Variables, stages, ADD, heredocs, remote/named contexts and unsupported flags remain unassessed. No build, destination validation or daemon access.

Automation

This tool runs in your browser. No upload API or MCP endpoint is available.