5 Free Browser-Based Dev Tools: GraphQL Formatter, Docker Compose Validator, Dockerfile Linter, and More

I just shipped 5 new tools to

Paste any GraphQL operation and get:

• 
  Pretty-print — consistent indentation


• 
  Minify — strips comments and whitespace for smaller request payloads


• 
  Validation — brace/parenthesis balance check


• 
  Operation detection — lists all named query, mutation, subscription, fragment
  

Useful for quick query cleanup before pasting into code reviews or API docs.

2. Protobuf (.proto) Formatter & Validator

Paste your docker-compose.yml to catch:

• Missing services section


• Services without image or build
  


• Invalid port mappings (80:80, 127.0.0.1:8080:80, 53:53/udp, ranges…)


• 
  depends_on referencing non-existent services


• 
  Circular dependency detection (A→B→A)


• Unknown restart policies
  

# This will flag errors:

services:

  web:

    ports:

      - "abc:xyz"       # invalid port

    depends_on:

      - missing_service  # unknown service

4. Dockerfile Analyzer & Linter

Paste raw email headers and instantly get:

Authentication Results

SPF   ✅ pass

DKIM  ✅ pass

DMARC ✅ pass

Phishing investigation often starts here — a failed SPF or DKIM check is a red flag.

Phishing Signals

• 
  Reply-To domain ≠ From domain — classic impersonation trick


• Return-Path domain mismatch


• Spam score / X-Spam-Flag detection

Routing Trace

Parses all Received: headers to show each hop the email traveled through, including originating IP addresses.

Three Tabs

1. 
   Summary — From/To/Subject/Date/Message-ID + auth status


2. 
   Routing — hop-by-hop trace with IP addresses


3. 
   All Headers — raw dump of every header field

Handy when your security team needs to quickly triage a suspicious email without spinning up a full mail analysis tool.

Implementation Notes

All five tools follow the same constraints:

• 
  Vanilla JS, single HTML file — no bundler, no framework, works offline


• 
  80+ Node.js assert tests — core logic is extracted and tested independently of the browser


• 
  No external YAML/parsing libraries — the Docker Compose validator uses a custom line-by-line indent parser

DevNestio now has 172 tools in total. If there's a utility you'd find useful, drop a comment — I'm always looking for the next one to build.