EncodersBase64 and URL encode/decode in one place — instant, client-side conversion.JWT DecoderDecode JWT header & payload, inspect claims, optionally verify HS256 signatures.JSON FormatterValidate, pretty-print, and visualize JSON with syntax highlighting.Mermaid LiveWrite Mermaid diagrams and see them render live — pan, zoom, export, and share.MindmapBuild mindmaps with keyboard shortcuts — saved to local storage, export PNG/SVG/JSON.C4 DiagramsWrite Structurizr DSL and render C4 context/container/component diagrams — saved to local storage.ExcalidrawHand-drawn whiteboard — sketch shapes, text, and freedraw; export PNG/SVG. Runs fully in-browser.
publicHTML Preview

HTML Preview

Render an HTML file from a GitHub URL, or paste raw HTML directly. Runs live in a sandboxed frame — fully client-side, like htmlpreview.github.io.

Accepts github.com/<owner>/<repo>/blob/<branch>/<path> or a raw.githubusercontent.com URL. Private repos won't load here — copy the file's HTML and use the Paste tab instead.