Free Developer Tools That Run in Your Browser

Format a JSON response, test a regular expression against real input, decode a JWT, or find out when a cron schedule will run next. These developer tools cover the small jobs that come up many times a day: formatting and validating data, beautifying and minifying code, encoding and hashing, and quick networking and web references.

Everything runs locally in your browser tab. The JSON, tokens, SQL and log lines you paste are processed on your own machine and are not sent to our servers, which matters when the input holds API responses, customer records or access tokens. There is no signup, no rate limit and nothing to install.

A few related tools live in other sections: the Base64 encoder and decoder, the Unix timestamp converter and the YAML to JSON converter are in Converters, and the UUID generator is in Generators.

28 free tools in this category. All run in your browser with no signup.

JSON, SQL, XML and YAML formatters

Paste messy or minified data and get it indented and highlighted. The JSON and XML formatters also tell you when the input is invalid, and the YAML formatter flags tabs and common indentation mistakes in Kubernetes and CI files.

JSON Formatter & ValidatorFormat, validate and beautify JSON online.SQL FormatterFormat and beautify SQL for MySQL, PostgreSQL, SQL Server and more, with your choice of indent and keyword case, or minify a query to one line.XML FormatterBeautify or minify XML and check it for errors with the line and column of the first problem.YAML FormatterFormat and validate YAML online.

Regex, diff, JWT and cron tools

Test a regular expression with live match highlighting and capture groups, compare two versions of a text line by line or word by word, decode a JWT's header and payload, and translate a cron expression into plain English with its next 10 run times.

Regex TesterTest JavaScript regular expressions with live match highlighting, capture groups, named groups and match indexes.Diff CheckerCompare two texts and see every added, removed and changed line side by side, with word-level highlights and options to ignore whitespace or case.JWT DecoderDecode a JSON Web Token to read its header, payload and expiry, then verify the signature with a secret or public key, all in your browser.Cron Expression ParserExplain any cron expression in plain English, see the next 10 run times in your time zone or UTC, and build schedules with a quick builder.

Beautify and minify HTML, CSS and JavaScript

Beautify minified code so you can read and debug it, or minify your own code to cut its file size before you ship it. The JavaScript minifier keeps strings, regular expressions and template literals intact.

HTML BeautifierBeautify minified or messy HTML with clean indentation.JavaScript BeautifierBeautify minified or messy JavaScript with readable indentation.CSS BeautifierBeautify minified CSS into clean, indented rules.CSS MinifierMinify CSS online and see the bytes saved.HTML MinifierMinify HTML online without gluing words together.JavaScript MinifierMinify JavaScript online with Terser.

Hash generators, encoders and decoders

Generate an MD5, SHA-1, SHA-256 or SHA-512 hash of text or a file to check a download, percent-encode a URL or query string, or escape special characters as HTML entities.

Hash GeneratorGenerate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes from text or files, add an HMAC key, and check a checksum, all in your browser.URL Encoder / DecoderEncode or decode URLs and query strings with encodeURIComponent, encodeURI, strict RFC 3986 or form rules, plus a URL parser and query string builder.HTML Entity Encoder / DecoderEncode text as named, decimal or hex HTML entities, or decode entities back to characters, with a searchable reference table of common entities.

Networking: subnets, ports, DNS and MAC addresses

Get the netmask, network and broadcast address and usable host range for any IPv4 address and CIDR prefix, look up what a port number is used for, check DNS record types with examples, or find the manufacturer behind a MAC address.

IP Subnet CalculatorCalculate IPv4 subnets from an IP and CIDR prefix or netmask: network, broadcast, wildcard mask, host range, usable hosts and a subnet splitter.Port LookupLook up any TCP or UDP port number or service name, from HTTP 80 and SSH 22 to MySQL 3306, with the protocol, what it does and whether IANA assigns it.DNS Record TypesEvery DNS record type explained with zone-file examples and type numbers: A, AAAA, CNAME, MX, TXT, NS, SOA, SRV, CAA, HTTPS and DNSSEC records.MAC Address LookupFind the manufacturer of any MAC address from the full IEEE registry, in any format, with flags for randomized, multicast and broadcast addresses.

HTTP status codes, MIME types and other references

Searchable references for HTTP status codes, MIME types by file extension and the ASCII character set, plus a parser that turns any User-Agent string into a browser, operating system and device type.

HTTP Status CodesEvery HTTP status code from 100 to 511 with its RFC 9110 name and meaning, plus common nginx and Cloudflare codes, searchable by code or keyword.MIME Type LookupFind the MIME type (Content-Type) for any file extension, or the extensions for a MIME type, and copy it in one click.User Agent ParserSee your own user agent string and decode any UA into browser, version, OS, device type and bot, including Chrome on iPhone, Samsung Internet and AI crawlers.ASCII TableASCII table with decimal, hex, octal, binary and HTML codes for all 128 characters, plus Windows-1252 extended codes 128 to 255 and a search box.

Markdown, TypeScript types and placeholder images

Write Markdown with a live preview and export it as HTML, generate TypeScript interfaces from a sample JSON object, or make placeholder images in any size for mockups and layouts.

Markdown PreviewWrite Markdown and see a live preview side by side.JSON to TypeScript ConverterConvert JSON to TypeScript interfaces or type aliases, merging array items into optional fields and unions, with export and readonly options.Placeholder Image GeneratorGenerate a placeholder image at any size from 1 to 4096 px with your colors and text.

Frequently asked questions

Why is my JSON invalid?

The usual causes are a trailing comma after the last item, single quotes instead of double quotes, keys without quotes, comments, and values like undefined or NaN that JSON does not allow. Paste the text into the JSON formatter: the error message points to the approximate position where parsing failed, so fix that spot and validate again.

What does */5 * * * * mean in a cron expression?

It means every 5 minutes. The five fields are minute, hour, day of month, month and day of week. A value of */5 in the minute field means every fifth minute (0, 5, 10 and so on), and * in the other fields means every value. The cron expression parser explains any expression in plain English and lists its next run times.

Is it safe to paste a JWT into an online decoder?

Only if the decoder works in your browser. The JWT decoder here reads the token on your own device, so it is not sent to our servers. Decoding only reads the header and payload; it does not check the signature, so never trust decoded claims until your server has verified the token.

What is the difference between minifying and beautifying code?

Minifying removes comments, whitespace and line breaks so a file downloads faster, and the code still runs the same way. Beautifying does the opposite, adding indentation and line breaks so a person can read it. Keep readable source in your project and serve minified files to visitors.

Guides

See every tool on ClickSolveTools, A to Z