Guides
Two kinds of writing live here. In-depth guides explain how a format or a process actually works, so they are worth reading whether or not you ever open one of our tools. Category roundups are the practical companion: which tool to reach for, and why.
In-depth guides
Longer explainers about formats, codecs and the trade-offs behind a conversion. New ones are published a few at a time rather than all at once.
- Lossless vs Lossy Audio: What Is Thrown Away, and Can You Hear It
What a psychoacoustic encoder actually removes, why re-encoding a lossy file compounds the damage, and how to pick a bitrate you will not regret.
- Resolution vs Bitrate: Which One Is Making Your Video Look Bad
Why a 4K file can look worse than a 720p one at the same size, what a bitrate actually buys, and how to tell which of the two is failing you.
- What DPI Actually Means (And Why Resizing Does Not Change It)
A print shop asks for 300 DPI and your file has none of that information. What the number really is, where it lives in the bytes, and when it matters.
- PNG vs JPG vs WebP vs AVIF: Picking a Format by Content
Four formats, two different models of a picture. Which suits photos, screenshots, logos and transparency, and why the newest is not automatically the best.
- PDF/A vs PDF: Archival Formats Explained
Why an archive rejects an ordinary PDF. What PDF/A forbids, what the parts and conformance levels mean, and which everyday PDF edits quietly break it.
- How Client-Side File Processing Works (And Why It Is Private)
What really happens to a file you drop on a web page that never uploads it: the File handle, the WebAssembly codec, and what does cross the network.
- Choosing a Bitrate for Voice vs Music
Why 40 kbps is fine for a lecture and ruins a song. What a bitrate actually buys, which content survives a low one, and what to change instead.
- Why Video Re-encoding Loses Quality (and When It Doesn't)
Some video edits are free and some cost quality every time. What re-encoding does to the frames, and how to tell which kind of edit you are about to make.
- HEIC vs JPG: What Actually Changes When You Convert
HEIC and JPG both discard detail, but not the same detail. What a conversion really costs: a second lossy pass, bit depth, transparency and metadata.
Category roundups
One per category: every tool we have in it, grouped by the job you are trying to do, with a "which one should I use" table at the end.
- Best Free Online Audio Tools: A Complete Guide to Converting, Editing and Fixing Audio Files
A complete guide to converting, cutting, boosting and cleaning up audio for free in your browser — MP3, WAV, M4A, FLAC and more. 30 tools compared.
- Best Free Online Calculators: A Complete Guide to Unit, Date, GPA, BMI and Other Everyday Math Tools
A complete guide to unit conversion, date math, GPA, BMI, tips and more — 12 free calculator and converter tools compared, with a which-tool table.
- Best Free Online Generators & Design Tools: QR Codes, CSS, Charts, Screenshots and More
A complete guide to QR/barcode generators, CSS builders, chart makers and other free design generator tools — 18 tools compared, with a which-tool table.
- Best Free Online Image Tools: The Complete Guide to Converting, Compressing and Editing Photos
A complete guide to converting, compressing, cropping and editing photos for free in your browser — JPG, PNG, WebP, HEIC and more. 42 tools compared.
- Best Free Online PDF Tools: The Complete Guide to Editing, Compressing, Converting and Securing PDFs
A complete guide to merging, splitting, compressing, converting and securing PDFs for free in your browser — no upload, no watermark. 28 tools compared.
- Best Free Online Text Tools: A Complete Guide to Formatting, Analyzing and Converting Plain Text
A complete guide to formatting, analyzing, translating and converting plain text for free in your browser — case conversion, grammar, word counts and more.
- Best Free Online Video Tools: The Complete Guide to Converting, Compressing and Editing Video
A complete guide to converting, compressing, trimming and editing video for free in your browser — no upload, no watermark, no size limit. 28 tools compared.
- Free Online Developer Tools: The Complete Guide to Encoding, Hashing, Formatting and Sysadmin Utilities
A complete guide to 61 free browser-based developer tools — encoding, hashing, JSON/YAML/XML formatting, archives, SEO, and sysadmin utilities.
- Free Online Hardware Testers & Widgets: The Complete Guide to Testing Your Keyboard, Mouse, Screen and More
A complete guide to testing your keyboard, mouse, and monitor for dead pixels, plus timers and productivity widgets — 11 free tools compared.