Donaldson R F Free Developer Tools
Formatters, converters, generators and checkers for developers and system administrators: JSON, regex, hashes, DNS, cron, subnets and more.
62 free tools in this category. No sign-up, no limits.
JSON Formatter & Validator
Format, validate, and beautify JSON, with clear error messages.
Open tool →Base64 Encode / Decode
Convert text to Base64 or decode it back, instantly.
Open tool →Color Picker & Converter
Pick a color and get its HEX, RGB, and HSL values.
Open tool →URL Encoder / Decoder
Encode or decode special characters for safe use in URLs.
Open tool →HTML Entity Encoder / Decoder
Convert special characters to HTML entities and back.
Open tool →Hash Generator
Generate SHA-1, SHA-256, and SHA-512 hashes from any text.
Open tool →UUID Generator
Generate random UUID v4 identifiers, one at a time or in bulk.
Open tool →Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates.
Open tool →CSS Minifier
Strip comments and whitespace from CSS to cut file size.
Open tool →HTML Minifier
Strip comments and whitespace from HTML to cut file size.
Open tool →HTML Editor & Live Preview
Type or paste HTML and see the rendered result instantly.
Open tool →XML Sitemap Generator
Paste your page URLs and get a ready-to-upload sitemap.xml.
Open tool →CSV to Excel
Convert a CSV file into a proper Excel (.xlsx) spreadsheet.
Open tool →Excel to CSV
Convert the first sheet of an Excel file into a CSV file.
Open tool →JSON to XML
Paste JSON and get a corresponding XML structure.
Open tool →Split CSV
Split a large CSV file into smaller files by row count.
Open tool →Text to Binary Converter
Convert text to binary code, or decode binary back to text.
Open tool →Morse Code Converter
Convert text to Morse code, or decode Morse back to text.
Open tool →Split Excel
Split a large Excel spreadsheet into smaller files.
Open tool →Markdown to HTML
Convert Markdown to HTML.
Open tool →HTML to Markdown
Convert HTML to Markdown.
Open tool →CSV to JSON
Convert CSV to a JSON array of objects.
Open tool →JSON to CSV
Convert a JSON array of objects to CSV.
Open tool →Password Strength Checker
Check how strong a password is.
Open tool →JWT Decoder
Decode a JSON Web Token and view its header and payload.
Open tool →File Hash Calculator
Calculate the hash of a file.
Open tool →Subnet / CIDR Calculator
Calculate subnet mask, network range, and host count, for IPv4 and IPv6.
Open tool →HTTP Status Code Lookup
Look up the meaning of any HTTP status code.
Open tool →Regex Tester
Test a regular expression against text with matches highlighted.
Open tool →JSON Minifier
Remove whitespace from JSON to reduce its size.
Open tool →YAML ⇄ JSON Converter
Convert between YAML and JSON.
Open tool →Cron Expression Generator
Build and explain a cron expression.
Open tool →CSV Column Extractor
Extract or reorder specific columns from a CSV file.
Open tool →CSV Sorter & Deduplicator
Sort a CSV by any column and remove duplicate rows.
Open tool →CSV Merger
Merge multiple CSV files with the same columns into one.
Open tool →Bulk File Renamer
Rename multiple files at once using a pattern.
Open tool →URL Parser
Break a URL down into its protocol, host, path, and query.
Open tool →User-Agent Parser
Parse a browser User-Agent string into browser, OS, and device info.
Open tool →Excel Merger
Merge multiple Excel files (same columns) into one.
Open tool →IBAN Validator
Check whether an IBAN is correctly formatted and valid.
Open tool →.htaccess Redirect Generator
Generate .htaccess redirect rules for Apache servers.
Open tool →TSV ⇄ CSV Converter
Convert between tab-separated and comma-separated values.
Open tool →Hash Identifier
Paste a hash and see which algorithm it most likely comes from.
Open tool →Credit Card Number Validator
Check a card number with the Luhn algorithm, in your browser only.
Open tool →Checksum & CRC Calculator
CRC-32, Adler-32, MD5 and SHA checksums of any file or text, calculated in your browser.
Open tool →MAC Address Lookup
Find the manufacturer of a device from its MAC address using the IEEE OUI registry.
Open tool →JSON Diff Tool
Compare two JSON documents and see what was added, removed or changed.
Open tool →YAML Formatter & Validator
Validate YAML with line-accurate errors and reformat it with clean indentation.
Open tool →XML Formatter & Validator
Check XML is well-formed, then pretty-print or minify it.
Open tool →SQL Formatter & Minifier
Format SQL with readable indentation or minify it to one line.
Open tool →TOML ⇄ JSON Converter
Convert between TOML and JSON with clear error messages.
Open tool →.gitignore Generator
Combine templates for languages, frameworks, OS and editors into one .gitignore.
Open tool →HTML Table Generator
Build HTML tables in a grid or from pasted data and copy the HTML and CSS.
Open tool →PX to REM Converter
Convert CSS units: px, rem, em, pt, %, vw, vh and more.
Open tool →chmod Calculator
Work out Linux file permissions: octal, rwx form and the chmod command.
Open tool →JSON to TypeScript
Generate TypeScript interfaces and types from a JSON sample.
Open tool →Mock Data Generator
Generate fake test data in JSON, CSV or SQL: names, UK addresses, emails, phone numbers, dates and IDs. Choose columns and rows.
Open tool →MIME Type Lookup
Look up the MIME type (Content-Type) for any file extension, or find the extensions for a MIME type. Searchable list of common types.
Open tool →Common Ports Lookup
Look up well-known TCP and UDP port numbers and the services that use them, such as 22 SSH, 443 HTTPS and 3306 MySQL.
Open tool →XML to JSON Converter
Convert XML to JSON with clear error messages: choose attribute and text naming, keep arrays, and convert numbers. Runs in your browser.
Open tool →Cron Schedule Simulator
Next runs of a cron expression in server, UTC and your time zone, with skipped and repeated times at daylight saving changes.
Open tool →Server Region Latency Estimator
Estimate the theoretical round-trip time from your users to AWS, Google Cloud and Azure regions from distance alone, as a range. No pings, no measurements.
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