How to use Yellorn

Paste text or open a file

Open the editor and paste JSON, JSON Lines, XML, YAML, TOML, CSV, ASCII tables, SQL, or Python. Yellorn auto-detects the format and switches once it’s confident — or pick one yourself from the toolbar’s format selector.

For local files, drag one onto the editor or choose its format and select Open file. The picker works on phones and tablets too. Binary files decode locally in your browser — Parquet, Apache Arrow / Feather, Excel, MessagePack, CBOR, Protobuf, BSON, gzip — as do AI model files (Safetensors, GGUF), ComfyUI PNGs, and X.509 certificates (PEM, DER, PKCS#12 / PFX, PKCS#7, CSR). Nothing is uploaded.

The visualizer updates as you type: CSV, Parquet, and Excel open as a table; JSON, XML, and YAML open as a tree.

Repair broken input with Smart Format

Press Cmd + Shift + F (or Ctrl + Shift + F on Windows / Linux) to run Smart Format. It runs the format’s recovery ladder — 29 fix passes across JSON, XML, YAML, and CSV — then pretty-prints the result.

Every applied fix is labelled in the status bar (Auto-fixed: trailing-commas, single-quotes) so you consent to every transformation before publishing.

Convert between formats

Open the toolbar Format selector and pick a target format row marked Convert (or Convert (lossy)) to swap the active format. JSON ↔ XML ↔ YAML ↔ CSV ↔ Python is supported with structural-compatibility checks; lossy conversions surface a warning toast first. One Cmd + Z reverts both the text and the format together.

Share a payload or comparison

Click Share to copy a temporary 24-hour link, or open its options to add a password and choose a lifetime from 5 minutes to 7 days. The recipient gets a cloned editor or diff tab. A temporary copy is stored until expiry, so treat an unprotected URL as a capability that anyone with the link can open. After creating one, use Revoke in the same drawer to delete it early; this browser retains control of your recent links across reloads. Cloudflare's global edge caches can take about a minute to stop serving the copy everywhere.

Publish a payload as a mock REST endpoint

Sign in (free) and click Publish. Yellorn returns a global HTTPS URL anyone can GET / POST / PUT / PATCH / DELETE. The owner-only portal at /webhook/<slug> shows every request — method, headers, body, source IP, and timestamp.

Pick a canned response status (200, 401, 404, 429, 500, and others) and add optional custom response headers from the portal to simulate failure paths without redeploying anything.

Make the mock response dynamic

A published webhook can return live data instead of a fixed string. Wrap a Python-flavoured expression in {{ }} and it renders fresh on every request: {{ uuid4() }} for a new id, {{ now() }} for the current timestamp, {{ randint(1, 100) }} or {{ choice("active", "pending") }} for random values, and {{ request.ip }} to echo the caller.

After publishing, open the webhook portal and use Insert token above its payload editor. Request Sender has the same picker, autocomplete, and live preview. In the home editor, type {{ … }} directly before publishing.

Dispatch outbound HTTP requests

Open Request Sender from the account rail, compose a request (method, URL, headers, auth, body), and save it as a template for reuse. Every dispatch is logged with response details for 8 hours on Free, 1 day on Pro, or 3 days on Team.

Search with JMESPath

Open the search bar in the visualizer and type a JMESPath expression — for example, users[?age > `30`].name. The tree filters live with match counts and Prev/Next navigation.

Back up your tabs across devices

Cloud Backup lives in Settings: click Back up to Cloud to save your open editor tabs, then Restore from Cloud on any other signed-in browser. Replacing an existing cloud snapshot or your local tabs requires a second confirmation click. Palette, pane layout, and other UI preferences stay on this device. Tabs over your size quota are skipped, and a usage bar shows how much room you have left.

Normalize copy-pasted lists with Clean List

Paste a messy list — one item per line, padded comma-separated values, a single-column SQL or Markdown table, or a bracketed array — then open the Format menu in the editor toolbar and choose Clean List (under Minify). Yellorn collapses it to a compact comma list, ready to paste into a SQL IN (…) clause or anywhere else that needs tidy values.

Compare two payloads side-by-side

Click Compare in the tab bar footer, pick exactly two tabs, then Run Comparison (or right-click a tab and choose Compare with the active tab). Yellorn opens Monaco’s read-only diff editor with both payloads. JSON content is key-sorted before diffing so key reorderings don’t pollute the output — only real structural differences appear. Useful for API response regression testing, fixture consistency checks, and customer-payload triage.