ProToolBox

Code Snippet Tester — Pretty JSON & Sandboxed HTML Preview

Choose JSON for JSON.parse pretty-print or HTML for escaped source plus a sandboxed iframe (no scripts). Live stats, one-tap copy—no upload, no signup, no watermark.

Format JSON and preview HTML locally

Pretty JSON for APIs and logs; HTML mode shows safe source and a locked-down preview for layout checks.

1 Pick type · 2 Paste · 3 Run · 4 Copy

Snippet input

Output & preview

Try . More JSON tools: formatter · validator · HTML escape.

Runs in this tab only—no server upload, no signup, no watermark.

Paste a snippet—stats update as you type when Live is on.

What you will see: Pretty JSON or escaped HTML plus an optional iframe preview. Next: Run or Live.

Output appears here

Paste JSON or HTML or tap sample.

Next: HTML preview is not a JS playground—sandbox blocks scripts. For full fidelity use your app; for JSON use validator before production. · All tools

  • Works in your browser—runs on your device, not our servers
  • No upload required—your input stays in this tab
  • Free and instant
  • No account needed
  • Private by default—the same ProToolbox promise on every page

What this is for

Code Snippet Tester — Pretty JSON & Sandboxed HTML Preview helps you format, validate, and encode before paste: works in your browser, no account needed. JSON, YAML, Base64, URLs, escapes—check here first, then ship to PRs, Slack, or configs.

  • Re-validate after every payload edit
  • Copy from the panel—nothing leaves your device until you do
  • Local run for tokens and internal data
  • Green here, then paste into production paths

Security: Fast correctness pass only—secrets still go through your team’s review.

Why use a local snippet tester

Quickly sanity-check payloads and markup without pasting proprietary JSON into random sites. The HTML iframe stays sandboxed so scripts cannot run—ideal for static layout peeks.

How it works

  1. Pick JSON or HTML.
  2. Paste your snippet and click Run or enable Live.
  3. JSON: we JSON.parse then pretty-print. HTML: escaped source + sandboxed srcdoc.
  4. Copy output back into your editor or ticket.

FAQ

  • Why doesn’t my <script> run? The preview iframe uses sandbox="" with no allowances—by design.
  • Trailing commas in JSON? JSON.parse rejects them—match your runtime.
  • Large payloads? Turn off Live if the tab slows.

Bookmark this page for webhook payloads, CMS fragments, and quick JSON eyeballing—everything stays in your tab until you copy.

Tools in this category