#350 · Developer Tool

Docker Ignore Checker

Review .dockerignore rules for mistakes that can enlarge a build context or leak local files. The checker finds duplicates, negations with no earlier exclusion, absolute paths, suspicious secret omissions, and patterns that may exclude Dockerfile itself. It also tests an optional sample file list when supplied after a separator line.

Developer Input

Local input
Ad space

How to use this developer tool

  1. Paste the docker ignore checker source into the input area.
  2. Choose Check .dockerignore or press Ctrl/Cmd + Enter.
  3. Read the summary and warnings before copying or downloading the result.
  4. Test the final value in the system that will consume it.

What this developer tool does

Docker Ignore Checker converts the supplied text into a diagnostic result with concrete counts and structured export data. It keeps the original input in place so warnings can be traced back to the source.

The browser normalizes line endings for analysis, applies check specific parsing rules, and reports findings without executing containers or contacting remote servers.

A local diagnostic is useful for review, but it cannot replace the configuration limits and parsers used by the final server, proxy, browser, or Docker daemon.

Example

Load the sample and run the tool. The output reports the parsed structure or findings derived from the exact sample shown in the input panel.

node_modules
.git
.env
*.log
dist
node_modules
!dist/keep.txt
---FILES---
node_modules/a.js
src/index.js
.env
dist/app.js

Use cases

  • Review configuration during a code review.
  • Turn copied source text into a shareable diagnostic.
  • Catch formatting mistakes before integration testing.
  • Export structured evidence for documentation or issue reports.

Tips for reliable output

  • Paste the complete field or file when surrounding context affects parsing.
  • Keep secrets masked before sharing output.
  • Compare warnings with the software version used in production.
  • Retest after every source change.
  • Use the sample first to understand the expected input shape.

Processing details

All core check processing runs in Vanilla JavaScript. Text is read locally, parsed once, and rendered into a read-only output area with optional JSON or CSV exports when structured rows are available.

This focused browser implementation does not perform network negotiation, authenticate credentials, build images, read a filesystem, or emulate vendor-specific size limits.

Frequently asked questions

Does Docker Ignore Checker send my input to a server?

No. Its core processing runs in the browser and does not make a network request.

What happens when the input is malformed?

The page reports a focused error or warning and leaves the source text unchanged.

Can I use the downloaded result in a project?

Yes, but review it first because local parsing cannot reproduce every server, Docker daemon, or registry decision.

How does this page handle Unicode text?

Byte measurements use UTF-8, while parsers retain Unicode characters in readable output.

Is the result a standards or build-time guarantee?

No. It is a diagnostic result; the receiving server or an actual Docker build remains authoritative.

Output fields

FieldMeaning
SummaryWhat was processed
InterpretationWarnings and next checks
StatsTool-specific counts and timing