Yellorn Help Library
Field guides for the bugs you actually hit — each maps a symptom to its root cause and a copy-paste fix.
Debugging
Symptoms you can spot in the portal and how to fix them at the source.
Fix multipart/form-data 400 errors: boundary, CRLF & \r\r\n
RFC 2046 multipart parsers are strict about boundary delimiters and CRLF line endings. Here's how to spot boundary-prefix, LF, and \r\r\n bugs in Yellorn.
How to fix broken JSON from ChatGPT and other LLMs
LLMs almost never return clean JSON. Yellorn's Data Doctor strips the markdown fences, prose, and Python-isms that ChatGPT and Claude add, then shows exactly what it changed.
Concepts
How the underlying primitives work.
What is a mock API webhook (and how to make one free)
A mock webhook is a real URL that returns the response you define. Publish one from any payload in Yellorn, point your app at it, and watch requests arrive in an owner-only log.
JSON Lines (JSONL / NDJSON): what it is and how to use it
JSON Lines puts one JSON object per line, making it streamable and appendable where a single JSON array isn't. Here's what JSONL/NDJSON is, when to reach for it, and how to open it.
JSON vs YAML vs TOML vs XML: which format should you use?
JSON, YAML, TOML, and XML all describe structured data, but each wins at a different job. Here's how they compare on syntax, comments, and types — with the best use case for each.
What is a Parquet file & how to open one online?
Apache Parquet stores tabular data by column, not by row, which makes analytics queries fast and files small — but means you can't just open it in a text editor. Here's what it is and how to read one.
Guides
Longer walkthroughs for specific workflows.
How to fix broken or invalid JSON online
Yellorn's Data Doctor auto-repairs the most common ways JSON breaks, then tells you exactly what it changed — so nothing is reshaped behind your back.
Convert JSON to CSV, YAML, XML, TOML, or Python online
One click turns JSON into CSV, YAML, XML, TOML, NDJSON, or Python — and back. Yellorn flags lossy conversions before they happen, so you're never surprised.
View Parquet, Excel & binary files online — no upload
Open binary data files — Parquet, Excel, Arrow, MessagePack, CBOR, Protobuf, BSON, gzip — as a readable JSON tree or table. Everything decodes locally in your browser; the file never leaves your machine.
Inspect AI model files: Safetensors, GGUF & ComfyUI
Read the metadata inside AI model files without downloading gigabytes of weights. Yellorn decodes the Safetensors / GGUF header and the ComfyUI workflow locally — just the structure, never the tensor data.
Capture, inspect, and replay webhook requests
Point a provider at your Yellorn capture URL, see exactly what it sent, then replay that request to your own handler — or relay it to another service — straight from the request log.
Dynamic mock API responses: UUIDs, timestamps & more
Static mock responses get boring fast. Dynamic tokens let your webhook return a fresh UUID, the current timestamp, a random value, or an echo of the incoming request — computed at the moment each request is served.
Back up and restore your workspace across devices
Open Settings, hit Back up to Cloud, and your editor tabs follow you to any other signed-in browser. Here's what's backed up, what stays local, and how quota works.
Normalize messy lists and table columns with Clean List
Clean List turns any copy-pasted list shape — newline-delimited, comma-padded, SQL table column, Markdown column, bracketed array — into a single compact comma list, ready for SQL, code, or anywhere else.
Remove empty, null & blank values from JSON online
One click drops every key, item, or column whose value is empty — null, "", [], or {} — while keeping meaningful zeros and false. Works on JSON, YAML, XML, TOML, JSON Lines, CSV, and ASCII tables, right in your browser.
How to decode a PEM, PFX, CRT, or CSR certificate online
Yellorn decodes every X.509 PKI file type in your browser — no upload, no server. Drop a certificate and get expiry status, fingerprint, and algorithm details at a glance.
View JSON online as an interactive tree, graph, or table
Stop scrolling raw text. Yellorn renders your data as a collapsible tree, a relationship graph, or a sortable table — and you switch views with a single shortcut.
Compare and diff two JSON files online
Spot exactly what changed between two API responses or fixtures. Yellorn key-sorts JSON before diffing, so a reordered key never appears as a false difference.
Send HTTP requests online: a browser-based REST client
A lightweight, Postman-style REST client that runs in your browser. Build a request, send it, save it as a reusable template, and review the full response.
Search and query large JSON with JMESPath online
Stop hunting through nested JSON by hand. A JMESPath query filters the tree live — extract every email, find items matching a condition, or jump between matches.
Format SQL online: MySQL, Postgres, BigQuery & more
Turn a one-line, copy-pasted, or minified query into clean, readable SQL. Yellorn formats across the common dialects and repairs markdown fences and smart quotes first.
Decode & encode Base64, URL, Hex & HTML entities online
Got an opaque blob from a log, JWT, or webhook? Yellorn's Raw Text transforms decode and encode Base64, URL, hex, HTML entities, and escapes locally — and Smart Format auto-detects which one you need.
Format & beautify XML online: pretty-print or minify
Turn a one-line or copy-pasted XML blob into clean, indented markup. Yellorn's Data Doctor repairs unclosed tags, unescaped ampersands, and fences first — then pretty-prints, all in your browser.
How to fix and format YAML online
YAML breaks on invisible things — a tab where spaces are required, a smart quote, a stray BOM. Yellorn's Data Doctor repairs the common YAML mistakes and reformats, then tells you exactly what it changed.
Can't find your problem?
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