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Markdown Preview Lab

Edit Markdown while comparing GitHub-, Qiita-, and Zenn-style previews in your browser.

View on GitHub
Local processing
About your filesFiles and content selected in this tool are processed in your browser and are not uploaded to a Browser Kitty backend.
Operation demo See the basic workflow in a short video.

About this tool

Markdown Preview Lab is an editor focused on comparing how the same Markdown may look across publishing destinations. Switch among GitHub-, Qiita-, and Zenn-style previews and compare two styles side by side.

Compatibility checks flag syntax that may behave differently between platforms and can jump to the relevant Markdown line. Drafts are automatically stored in localStorage so you can continue editing later.

Good for

  • Preview a README in a GitHub-like style before publishing it
  • Adjust Markdown for Qiita or Zenn while comparing rendering differences
  • Write long Markdown drafts locally with autosave and synchronized previews

What it can do

Key capabilities available in this tool.

How to use

  1. Select Open tool and enter Markdown in the editor pane.
  2. Choose GitHub, Qiita, Zenn, or another style for Preview A.
  3. To compare renderings, switch to comparison mode and choose another style for Preview B.
  4. Review compatibility scores and warnings, and jump to flagged lines when needed.
  5. Copy the finished Markdown or save it as a .md file with your chosen filename.

Supported

  • Preview styles: GitHub, Qiita, Zenn, Standard, Minimal, Print, and Custom CSS.
  • Comparison mode: synchronized scrolling across editor, Preview A, and Preview B.
  • Editing helpers: bold, italic, headings, links, code, lists, undo, and redo.
  • Storage and files: localStorage autosave, Markdown file import, .md export, and clipboard copy.

Limitations and notes

  • The GitHub, Qiita, and Zenn previews are approximations and do not guarantee pixel-identical rendering to the live services.
  • Compatibility scores and warnings are heuristic guidance, not official platform validation.
  • Drafts are stored in localStorage and are removed if browser site data is cleared.
  • Advanced platform-specific syntax or future platform changes may not be fully reproduced.

Frequently asked questions

Is my Markdown sent to a server?

No. Editing, preview, compatibility checks, autosave, and file export are handled in your browser.

Will it look exactly the same as GitHub, Qiita, or Zenn?

Exact matching is not guaranteed. Use the previews to spot likely differences before publishing.

Are drafts saved automatically?

Yes. Drafts are saved to localStorage and restored the next time you open the tool.

Can I compare two preview styles at once?

Yes. Comparison mode shows Preview A and Preview B together with synchronized scrolling across all three panes.

Offline version and source code

The GitHub version is a single HTML file with no runtime CDN dependency. Save it locally to keep editing and previewing Markdown offline.

View source on GitHub

Use together

Useful next steps and companion tools, organized around the workflow.

Transform text Developer Toolbox Encode or transform URLs and text used in Markdown. Organize links Temporary Links Keep several URLs used in a document together temporarily. Inspect the writing Text Inspector Check counts, frequent words, and long sentences in the Markdown text before publishing.