How to Hash a Password with Bcrypt
What bcrypt does, how to pick a cost factor, how verification works with the salt, and how to generate or check a bcrypt hash in your browser for testing.
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Encoding, formatting, parsing — guides with working code.
How to Check Color Contrast for WCAG
Check whether text and background colors pass WCAG AA and AAA, what the 4.5:1 and 3:1 ratios mean, when text counts as large, and how to fix colors that fail.
How to Compress a PDF to Under 1 MB
Get a PDF under 1 MB for email, forms, and upload portals: pick the right compression level, check the result, and fix files that stay too large. In-browser.
How to Convert CSV to JSON (and Back)
Turn a CSV export into a JSON array of objects, handle tabs, semicolons, and quoted fields, and convert JSON back to CSV for spreadsheets. Runs in your browser.
How to Format and Validate XML Online
Pretty-print messy XML, find the exact error in malformed markup, and minify it for transport. What a formatter changes and the XML mistakes it catches first.
How to Compress a PDF Under 200 KB
Shrink a PDF below 200 KB for job portals and online forms: compress it in the browser, check the size, and what to do when the file is still too large.
How to Convert Markdown to HTML
Turn Markdown into clean HTML with a live preview, see how each piece of syntax maps to a tag, and convert HTML back to Markdown, including GFM tables.
Merge PDF Files on Your Phone Without an App
Combine PDFs on Android or iPhone in the mobile browser, with nothing to install. Pick files in order, merge, download, and fix the common mobile snags.
How to Convert cURL to JavaScript fetch()
Turn any cURL command into a JavaScript fetch() call. How the common flags map to fetch options, with worked examples for headers, JSON bodies, and auth.
How to Convert HEX to RGB (and Back)
Convert HEX color codes to RGB and back with a clear formula, a worked example, and a reference table of common values. Plus when to use each format in CSS.
How to Make a CSS Gradient: Linear, Radial, Conic
Write CSS gradients by hand or generate them visually. The syntax for linear, radial, and conic gradients, with copy-paste examples and common pitfalls.
How to Format SQL Online for Readable Queries
Format and beautify SQL queries online in seconds. What a formatter changes, why consistent style reduces bugs, and dialect notes for MySQL and PostgreSQL.
How to Generate an SHA-256 Hash Online
Generate MD5, SHA-1, and SHA-256 hashes online and understand what each is for. Why SHA-256 is the safe default and why hashing is not encryption.
How to Convert PNG, JPG, WebP, and AVIF Images
Convert PNG, JPG, WebP, BMP, and AVIF images in the browser, with Python Pillow, and ImageMagick — with format choice guidance for web, print, and transparency.
How to Convert an Image to PDF (Free)
Convert JPEG, PNG, and WebP to PDF in the browser, on the command line, and with Python — including how to combine multiple images into a single PDF.
How to Convert Between Time Zones
Convert times between time zones in the browser, Python, and JavaScript, with DST handling, UTC offsets, and the naive datetime trap that gives wrong results.
How to Generate a QR Code (Free)
Generate QR codes for URLs, text, email, WiFi, and contact cards — in the browser and with code using Python and JavaScript.
How to Check SSL Certificate Expiry
Check when an SSL certificate expires using OpenSSL, curl, and browser tools — plus how to set up automated expiry alerts before it causes downtime.
How to Look Up DNS Records
Look up A, AAAA, MX, CNAME, TXT, and NS records using dig, nslookup, and online tools — with examples for every record type.
How to Resize an Image Without Losing Quality
Resize images for web, email, and social without visible quality loss — with the right resampling method, format choice, and tools for every workflow.
What Does Your IP Address Reveal?
Your IP address shows your ISP, approximate city, and country to every site you visit. It doesn't show your name or street address. Here's what's visible.
How to Add Page Numbers to a PDF for Free
Add automatic page numbers to any PDF — in a browser without installing anything, or with Python and command-line tools for batch processing.
How to Calculate Percentage Change and Increase
Formulas for percentage change, percentage difference, and percentage of a total — with JavaScript, Python, and Excel examples for each.
Compress Images for the Web Without Losing Quality
Reduce image file sizes for faster page loads — with the right format, quality settings, and tools for JPEG, PNG, and WebP compression.
How to Convert SVG to PNG: Browser, CLI, and Code
Convert SVG files to PNG images at any resolution — in a browser, with Inkscape or ImageMagick from the terminal, or programmatically with Node.js and Python.
How to Count Words, Characters, and Lines
Count words, characters, sentences, and reading time in any text — with JavaScript, Python, and command-line one-liners for every counting task.
Generate a Secure Random Password in JS and Python
Generate cryptographically secure random passwords in JavaScript, Python, and the command line — with configurable length, character sets, and entropy analysis.
How to Generate a UUID in JavaScript and Python
Generate UUID v4 identifiers in JavaScript (browser and Node.js), Python, and the terminal — with explanations of UUID versions and when to use each.
How to Format and Validate JSON Online
Pretty-print minified JSON, validate syntax, and fix common JSON errors — with examples of the most frequent mistakes and how to spot them.
How to Minify CSS for Production
Minify CSS with build tools or a one-line command — and what minification actually does to your stylesheets.
How to Calculate the Days Between Two Dates
Calculate the number of days between any two dates in JavaScript, Python, and Excel — with working formulas and an explanation of why date math is tricky.
Convert YAML to JSON: CLI, Python, and JavaScript
Convert YAML to JSON in Python, JavaScript, or one command — with working code examples and conversions back to YAML.
How to Base64 Encode an Image for CSS and HTML
Embed images directly in CSS and HTML using Base64 data URIs — when it helps performance, when it hurts, and how to generate them.
How to Extract EXIF Data from a Photo
Read camera settings, GPS coordinates, and timestamps embedded in JPEG and TIFF files — using browser tools, Python, and command-line options.
Cron Expression for Every 15 Minutes (and More)
Cron syntax with copy-paste expressions for every 15 minutes, hourly, daily, weekly, and every other common schedule.
URL Encoding Special Characters: A Practical Guide
When and how to URL-encode special characters — with examples in JavaScript, Python, and a reference table of common encoded values.
Regex for Email Validation: What Actually Works
The right regex for validating email addresses — plus what regex can and can't check, and when to use a different approach entirely.
How to Compress a PDF Without Losing Quality
Reduce PDF file size without sacrificing text sharpness or image quality — online tools through command-line options.
How to Decode a JWT Without Verifying It
Read a JWT's payload without a secret key — with code examples in Python and JavaScript, and when it's safe.
How to Base64 Encode and Decode in Python
Base64 encode and decode strings, bytes, and files in Python using the built-in base64 module — with working code examples.