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.
- What a PDF Password Actually Protects (and What It Leaves in Plain Sight)
A PDF can carry two passwords that do very different jobs. Which one encrypts the content, which one is only a request, and what stays visible either way.
- Character Encodings: Why Your Text Turned Into Question Marks
What UTF-8 and Latin-1 actually do to bytes, where mojibake comes from, and why the same file opens correctly in one program and as garbage in another.
- Color Spaces: Why the Same Hex Code Looks Different Everywhere
What sRGB actually specifies, why a hex code is meaningless without it, and what a wide-gamut photo loses when a browser converts it.
- Frame Rate: What Changing FPS Really Does to Motion
Why 24, 30 and 60 fps feel different, why converting between them stutters, and what the fractional NTSC rates are actually doing in your files.
- Hashing vs Encryption vs Encoding: Three Things People Call Encrypting
Why Base64 protects nothing, why a hash cannot be reversed, and which of the three you actually need. With the parameters that make each one safe.
- How OCR Actually Works, and Why It Fails on Some Scans
What text recognition needs from a scan, why adding a text layer leaves the page looking identical, and the input problems no engine can fix.
- Loudness Normalization: What LUFS Is and Why Streaming Services Care
Why turning up the peaks does not make a podcast louder, what -16 LUFS means, and why every platform quietly re-levels what you upload.
- Subtitle Formats: SRT, VTT and the Ones Players Silently Ignore
Why a subtitle file works in VLC and does nothing in a browser, which formats hold text and which hold pictures, and what conversion cannot recover.
- What EXIF Metadata Reveals About Your Photos
Which fields a camera writes into a photo, why the GPS coordinates are precise enough to find a doorway, and what you lose by removing them.
- What Actually Happens When You Zip a File
What DEFLATE does to your bytes, why photos and video barely shrink, what store mode is for, and how a few megabytes can expand into terabytes.
- Why Two PDFs of the Same Document Differ Tenfold in Size
Where the bytes in a PDF actually go, why a scan is twenty times larger than an export, and which compression step is worth running on which file.
- Why Screenshots Look Bad as JPG
The same encoder that flatters a photograph destroys text and UI edges. What JPEG throws away, why PNG is often smaller here, and when to switch.
- 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.