Guides
The questions that come before the tool. Every answer here comes from files we opened and measured, not from a spec sheet.
- What is a HEIC file, and why won't it open?Your iPhone stopped saving JPEGs years ago. Here is what it saves instead, why almost every upload form rejects it, and what a conversion actually costs you.
- PNG, JPG, WebP or AVIF — which should you use?Four formats, one question that settles most of it: is the image a photograph, or is it flat colour, text and lines?
- Why your PDF is so large — and what actually shrinks itA 40 MB PDF and a 400 KB PDF can look identical on screen. The difference is almost never the text.
- MOV vs MP4 — what actually differsThey are closer than the different extensions suggest. Knowing how close tells you when a conversion is free and when it costs you picture quality.
- How background removal actually works — and when it failsNothing is being cut out. A model is guessing, pixel by pixel, how much of each one belongs to the subject. Once you know that, every strange result you have seen makes sense.
- Does AI upscaling add real detail?The short answer is no. The longer answer is more useful: it invents detail that looks right, and whether that helps depends entirely on what was wrong with your image in the first place.
- SRT vs VTT — which subtitle file do you need?Open both in a text editor and you will struggle to tell them apart. The differences are tiny, but one of them decides whether a web page will play your subtitles at all.
- What are stems — and can you really unmix a finished song?In a studio, stems exist before the mix does. Getting them out of a file that has already been mixed is a completely different operation, and it is worth knowing what you are actually being handed.
- Why won't my PDF open?"This file cannot be opened" covers at least five completely different problems. Telling them apart takes about ten seconds and saves you from trying the wrong fix.
- CSV vs Excel — what actually differsAlmost every confusing thing that happens to a CSV comes from one fact: a CSV file has no idea what its values mean. Excel guesses, and the guesses are where data gets damaged.
- Can AI summarise a document reliably?Sometimes, and the failures are specific enough to be worth learning. We tested four models on the same documents; two of them did not summarise at all.
- WAV vs MP3: which one do you actually need?One of these discards sound on the assumption you will not miss it. The other keeps everything and charges you about ten megabytes a minute for the privilege. Which is right depends entirely on what happens to the file next.
- What is a codec — and how is it different from MP4?Almost everything confusing about video files comes from a single distinction: the extension names the box, not the thing inside it. Separate those two and most of the mystery goes away.
- Why is my video sideways?The file is not damaged and your phone did not make a mistake. A portrait video is usually stored as a landscape picture with a note attached, and everything depends on whether the next program bothers to read the note.