ZIP Launch Lens — HTML5 Build Preflight

Catch common HTML5 packaging mistakes before uploading. ZIP Launch Lens checks one ZIP in your browser. No account, API key or installation.

Try it

1. Click Run tool, then try the clean or deliberately broken example.
2. Choose your own HTML5 ZIP to check its root entry page and supported literal asset references.
3. Use the findings to fix filenames and paths, then test the actual hosted game.

Checks include

• Root index.html, missing files and filename-case mismatches.
• Root-relative paths, duplicate or unsafe paths, supported ZIP structure and CRC checks.
• Literal HTML/CSS references and documented itch.io file/path defaults.

Private by design: selected ZIP contents stay in your browser. The tool does not execute games, change files, extract them to disk or fetch external asset URLs. Normal hosting access logs may exist. Reports can contain filenames and base URLs; review them before sharing.

Free browser tool / optional $9 batch pack

This working browser edition is free. Want repeatable checks for several builds? The ZIP Launch Lens Batch & CI Pack ($9 on Gumroad) adds a Node.js CLI for up to 50 ZIPs, JSON reports, strict mode, CI exit codes, editable source and 34 automated checks. Same checker core; no subscription. Node.js 22+ required, tested on Windows with 24.19.0. MIT licensed source.

Limits, honestly

Static heuristic preflight, not a complete HTML/CSS parser, security audit or runtime guarantee. It does not verify JavaScript-generated URLs/imports/fetches, srcset candidates, engine manifests, WASM dependencies, CORS, controls, audio or saving. No third-party engine export or customer build has been tested. The examples are synthetic.

Scanner caps: 50 MiB ZIP, 100 MiB expanded, 40 MiB per entry, 2,500 entries. Stored/deflated ZIPs only; no ZIP64, encryption or split archives. HTML/CSS above 1 MiB is skipped with a warning. Scanner limits can be lower than the host limits. Use a modern desktop browser supporting DecompressionStream deflate-raw; tested in current Chrome on Windows.

Made with AI assistance in code, text and design; cover artwork generated with Gemini. Screenshot shows the real tool with a synthetic broken example. Independent tool by Samet Ateşen; not affiliated with itch.io or Gumroad.