API Studio

API Studio is a Postman-style API client that runs entirely in your browser, with no account and no install. Build requests, organise them in collections, test them and run whole flows.

Features

Params synced with the URL, headers, JSON / text / form / multipart bodies with file uploads; collections with drag-to-reorder; import Postman, OpenAPI/Swagger and HAR; export to Postman
Bearer, Basic, API-key, OAuth 2 (PKCE, client credentials, password, auto-refresh) and AWS Signature v4 auth; environments with {{variables}} and masked secrets
HTTP, GraphQL (schema explorer) and WebSocket requests in tabs; live server-sent event streams
No-code tests, JSON Schema contract checks from OpenAPI, captures, sandboxed pm.* scripts, mock responses and a collection runner with CSV/JSON data
Response tree, raw view, headers, HTML/image preview, JWT decoding, history and cURL import/export

How to use it

Pick a method and enter a URL, or paste a cURL command into the URL bar.
Add params, headers, a body or auth; use {{variables}} from the active environment.
Press Send (Ctrl/⌘+Enter) and explore the response.

FAQ

Does my request go through your server?

No. The browser sends it directly to the API you enter. There is no proxy, and collections, history and environments are stored only in your browser.

What about APIs that block browser requests (CORS)?

Install the free API Studio companion extension from the tool: it sends your requests without CORS limits and lets you set headers like Cookie, Origin and User-Agent. It works only on this site and collects nothing.

Can I import my Postman collections?

Yes. Postman v2.0/2.1 collections import with folders, auth (including OAuth 2 and AWS) and variables, and their pm.* scripts run in a sandbox once you allow them. You can export back to Postman at any time.

Why does a request fail with a CORS error when it works in Postman?

Browsers only let web pages call APIs that allow it with CORS headers; desktop apps like Postman are not restricted. Enable CORS on your API, or use Copy as cURL to run the request from a terminal.

More developer tools

API Studio

Build, test and automate HTTP requests right in your browser.

API Studio: Build, test and automate HTTP requests: collections, environments, tests and a runner.

Diagrams

Draw cloud architectures and watch the data flow.

Architecture Builder: Draw cloud architectures and data flows with AWS, Azure, GCP and 1,000+ components.

CI/CD

See, edit and check your CI/CD pipelines.

Pipeline Studio: See and edit your Bitbucket pipelines as a metro map, with checks for mistakes Bitbucket would reject.

Data

Query, browse and edit data files and SQLite databases.

Database Studio: Query, browse and edit CSV, Excel, Parquet and SQLite files with SQL, right in your browser. Nothing is uploaded.

System Design

Simulate traffic through a system design and find its limits.

System Design Simulator: Design a system, send it traffic and watch where it melts: latency, errors and the bottleneck.

Team Knowledge

Every error your team has hit, and how it was fixed.

Error Memory: Search every error your team has hit and how it was fixed; log new ones with their fix.

Formatters & Beautifiers

Make messy payloads, queries and markup readable.

JSON & Log Formatter: Repair, beautify and deep-decode JSON, Python dicts and log lines.
SQL Formatter: Pretty-print queries for 12 SQL dialects.
XML / HTML Beautifier: Beautify or minify HTML and XML, with validation.
JSON Diff: Compare two payloads side by side or as a change list.
SQL Diff: Compare queries, scripts or schemas as SQL, with schema changes and the migration.
JQ / JSONPath: Filter JSON with jq or JSONPath expressions.

Encoders & Decoders

Look inside tokens, encodings and escaped text.

JWT Debugger: Decode tokens, check expiry and verify HMAC signatures.
Base64 / Hex / Binary: Convert text and files between Base64, hex and binary.
URL / Query Parser: Split, edit and rebuild URLs and query strings.
HTML & Unicode Entities: Encode and decode HTML entities and Unicode escapes.

Generators

IDs, hashes, keys, placeholder text and typed code.

UUID / ULID / Hash: Generate UUIDs and ULIDs; hash text or files.
Lorem Ipsum: Placeholder paragraphs, sentences or words.
RSA / EC Key Pair: RSA and EC key pairs as PEM or JWK, via WebCrypto.
Schema & Code Generator: Turn sample JSON into TypeScript, Zod, Go, Rust, SQL and more.

Converters

Move data between formats, times and color spaces.

Unix Timestamp ↔ Date: Convert Unix timestamps to dates and back.
Color Converter: HEX, RGB, HSL and OKLCH with WCAG contrast checks.
Cron Parser: Explain cron expressions and list upcoming runs.
Format Converter: Convert between JSON, YAML, TOML, XML and CSV.

API & Debugging

Reproduce requests, read errors and sanitise logs.

Log → cURL: Rebuild a runnable cURL from logs, HAR or fetch calls.
HTTP Status Codes: Status codes with causes and fixes.
Payload Redactor: Strip secrets and personal data before you share.
Regex Tester: Test patterns live and explain them token by token.