A curated collection of twelve free developer tools for formatting and converting data, encoding and decoding values, inspecting tokens, testing APIs and CORS, and generating hashes and IDs. All free, all client-side, no signup.
This is the Zovo collection of free developer tools — a single hub that gathers the small, sharp utilities you reach for dozens of times a day while building and debugging software. Instead of one heavyweight app, each tool does one job well: pretty-printing a JSON response, decoding a JWT to read its claims, encoding a string to Base64, escaping a URL, testing a regular expression, firing a live API request, diagnosing a CORS error, explaining a wall of HTTP headers, or generating a hash or a UUID. Together they cover the formatting, encoding, inspection, and testing chores that sit between you and shipping.
The collection is built for back-end and front-end developers, API integrators, QA engineers, students, and anyone who works with data interchange formats, tokens, and HTTP. Whether you are wiring up an integration, reproducing a bug from a log file, checking why a preflight request fails, or seeding a database with identifiers, these tools turn a fiddly, error-prone task into a paste-and-read operation. Each one is focused enough to learn in seconds and reliable enough to keep in a pinned tab.
Every tool here shares three promises. First, they are completely free — no trial, no credit card, no premium tier hiding the useful parts, and no usage limits. Second, they require no account and no signup; you open a tool and start working immediately. Third, they are client-side: formatting, decoding, encoding, hashing, and analysis all happen entirely in your browser, so the JSON payloads, access tokens, and secrets you paste never leave your machine and are never uploaded to a Zovo server. That privacy matters when the thing you are debugging is a production token or a customer record. The only tools that make a network request are the API Tester and CORS Tester — and those requests go to the endpoint you choose, by design, so you can see the real response. Pick a tool below, or read the workflow section to see how they chain together.
Clean up, validate, and convert the data formats you read and write every day.
Format, minify, and validate JSON with syntax highlighting, a tree view, diff compare, and JSON path lookups — pretty-print messy responses in one paste.
Open tool →Convert HTML into clean Markdown instantly, with support for tables, lists, headings, links, images, and code blocks. Runs client-side with no data sent to servers.
Open tool →Convert Unix timestamps to human-readable dates and back, with a live clock, batch conversion, timezone support, a millisecond toggle, and relative time.
Open tool →Translate text between the encodings and token formats that move data across the wire.
Base64 encode and decode text or files, with UTF-8 and URL-safe modes, auto-detect, and drag-and-drop file conversion — including Base64 back to a file.
Open tool →URL encode and decode text with encodeURIComponent and encodeURI modes, bulk processing, a URL parser, auto-detect, and component-level encoding.
Open tool →Decode and inspect JWT tokens to view the header, payload, and signature, and check expiration and issued-at times — all locally, so tokens stay in your browser.
Open tool →Test patterns, fire real requests, and decode the network errors that block a deploy.
Test and debug regular expressions in real time, with syntax highlighting, match groups, a common-patterns library, and a cheat sheet.
Open tool →Build and send HTTP requests, then inspect the response with JSON highlighting. Includes code generation for cURL, fetch, and Python, plus collections.
Open tool →Test Cross-Origin Resource Sharing headers, simulate preflight requests, debug CORS errors, and validate how an API endpoint is configured.
Open tool →Paste raw HTTP headers to instantly parse, categorize, and explain every one — covering security, caching, CORS, and content headers.
Open tool →Produce the hashes and identifiers you need for integrity checks, keys, and records.
Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes from text or files, with HMAC support, hash comparison, and file-integrity checks.
Open tool →Generate UUID v4, v1, and v7, with bulk creation up to 1000 at once, multiple format options, and UUID validation and parsing — all in your browser.
Open tool →Most debugging sessions follow the data as it moves, and this collection maps onto that path. When a response comes back unreadable, start by making it legible: paste it into the JSON Formatter and Validator to pretty-print and validate the body, and reach for the Epoch Time Converter when a field turns out to be a Unix timestamp you need to read as a real date. If you are turning a rendered page or rich text into docs, the HTML to Markdown Converter does the conversion in one paste.
When the problem is authentication or transport, drop down a layer. Decode the bearer token with the JWT Decoder to confirm the claims and that it has not expired, escape or unescape query parameters with the URL Encoder and Decoder, and translate binary or header values with the Base64 Encoder and Decoder. To reproduce the call itself, the API Tester sends a real request and shows you the status, headers, and body, and even hands you a cURL or fetch snippet. When the browser blocks that call, the CORS Tester simulates the preflight and the HTTP Header Analyzer explains exactly which security, caching, and CORS headers came back.
The last group covers the values you generate rather than inspect. Use the Regex Tester to build and verify a pattern against sample input before you paste it into code, the Hash Generator to produce or verify a checksum or HMAC, and the UUID Generator to mint identifiers for records, test fixtures, or keys. Read the response, decode the token, reproduce the request, then generate what you need — that is a full debugging loop without leaving your browser.
If you are not sure where to begin, match your goal to a tool:
Yes. Every tool in this collection is completely free to use with no trial, no credit card, and no hidden upgrade wall. There are no usage limits and no premium tier that locks the useful features. We build them as genuinely useful utilities, supported by the rest of the Zovo site, so you can format, decode, test, and generate without paying anything.
No. These tools run entirely in your browser using JavaScript, so the JSON you format, the JWT you decode, the text you encode, and the headers you analyze are all processed locally on your device and never uploaded to a Zovo server. This matters when you are pasting access tokens, API payloads, or anything sensitive. The only external request is a standard Google Analytics page-view tag for traffic counts. The exception is the API Tester and CORS Tester, which by design must send a request to the URL you choose so they can show you the real response — those requests go to the endpoint you type, not to us.
The processing tools work offline once the page has loaded, because formatting JSON, decoding a JWT, encoding Base64 or URLs, generating a hash or UUID, and analyzing pasted headers all happen locally in your browser with no server round-trips. The exceptions are the API Tester and CORS Tester, which need a live network connection to send a real HTTP request to the endpoint you are testing and read its response.
Match the tool to the job. To inspect a JSON Web Token, use the JWT Decoder to read its header, payload, expiry, and issued-at claims. To pretty-print or validate a raw JSON response, use the JSON Formatter and Validator. To send a live request and see the status, headers, and body, use the API Tester. To debug a cross-origin error, use the CORS Tester to simulate the preflight, and the HTTP Header Analyzer to understand the security, caching, and CORS headers in the response.
No. There is no account, no signup, and no login. You open any tool and start working immediately. Because everything runs client-side, there is nothing to register and no profile to manage; nothing you enter is tied to an identity or stored on a server.