How to use Yellorn
Seven steps from opening a file — text or binary, across 20 formats — to publishing your first mock REST endpoint, plus the keyboard shortcuts that earn their keep.
Walkthrough
Each step builds on the previous one — but each one stands alone, so feel free to jump ahead.
Paste text or drop a file
Open the editor and paste JSON, JSON Lines, XML, YAML, TOML, CSV, SQL, or Python. Yellorn detects the format automatically and switches the active plugin once confidence crosses 90%. You can override the detection from the format selector in the toolbar.
Or drag a file onto the editor to open it. Beyond text formats, Yellorn decodes binary files locally in a worker — Parquet, Apache Arrow / Feather, Excel (
.xlsx/.xlsm/.xls), MessagePack, CBOR, Protobuf, BSON, and gzip — plus AI model files (Safetensors, GGUF) and ComfyUI workflows embedded in a generated PNG. Nothing is uploaded; the file never leaves your browser.The visualizer (Tree / Graph / Table) updates as you type — every plugin declares which views it supports, so CSV, Parquet, and single-sheet Excel default to Table while JSON / XML / YAML default to Tree.
Repair broken input with Smart Format
Press Cmd + Shift + F (or Ctrl + Shift + F on Windows / Linux) to run Smart Format. It applies the format-specific recovery ladder — 15 fixes for JSON, 5 for XML, 6 for YAML, 3 for 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
Click Convert to… in the editor toolbar 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.
Publish a payload as a mock REST endpoint
Sign in (free) and click Publish in the toolbar. Yellorn returns a global HTTPS URL anyone can GET / POST / PUT / PATCH / DELETE against. The owner-only portal at
/webhook/<slug>shows every incoming request with method, headers, body, source IP, and timestamp.Configure the canned response status code (200 / 401 / 429 / 500) from the portal to simulate failure paths without redeploying anything.
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 full response details for 8 hours.
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.Sync your workspace across devices
Cloud Backup is in Settings: manually back up your tabs, palette, and pane split, then restore them on any other signed-in browser.
Keyboard shortcuts
Every shortcut works on macOS (Cmd) and Windows / Linux (Ctrl); the ⌘ glyph is shown for compactness.
| Shortcut | Action |
|---|---|
| ⌘⇧F | Smart Format (full recovery) |
| ⌥⇧F | Simple Format (semantic preserve) |
| ⌥⇧C | Compress (minify) |
| ⌘⇧T | Cycle visualizer view (Tree / Graph / Table) |
| ⌥⇧W | Close the active tab |
| ⌘⇧H | Open the Webhooks dashboard |
| ⌘⇧D | Cycle to next color palette |
| ⌘Z | Atomic undo (text + format together) |
| ⌘F | Open Monaco's find widget |
Where to go next
Pick whichever surface matches what you came here for.