Guides

Practical explanations of file formats, compression and privacy — written for people who just want their file to work, not a computer science lecture.

• Why is my PDF upside down?A PDF page carries a rotation instruction separate from its content, which is why turning it in a viewer often does not save. What is actually happening, and how to fix it for good.
• What audio bitrate should you use?The number in the quality dropdown decides both file size and how good it sounds. What it measures, what each setting is genuinely for, and the one rule that catches everyone out.
• Lossless vs lossy audioFLAC and WAV keep everything. MP3 throws things away permanently. Which to keep, which to send, and why converting back does not undo anything.
• MP4 vs MOV vs MKVThree file extensions that frequently contain identical video. The container-versus-codec distinction explains why one conversion takes two seconds and another takes ten minutes.
• WebP vs AVIF vs JPG vs PNGFour formats, genuinely different jobs. What each one is good at, where each falls down, and a straight answer for photos, logos, screenshots and web images.
• Why won't my iPhone photos open on Windows?Your photos are almost certainly HEIC — a format Apple adopted in 2017 that most Windows software still cannot open. Three fixes, and the one worth doing permanently.
• How to get a photo under 5MB for emailAttachment limits are smaller than advertised because of how email encodes files. Here are the two levers that actually shrink a photo, and which one to use first.
• Why do my photos come out sideways?The same photo looks right on your phone and wrong on your laptop. The cause is one number inside the file that some software reads and some ignores.
• How to make images load faster on your websiteImages are usually most of what a page weighs. Four changes, in order of impact, and the one that fixes layout jumping rather than load time.
• Scanning documents with your phone into one PDFPhotographing paper beats a scanner for speed. How to shoot pages that read cleanly, and how to turn them into one document instead of eight attachments.
• Image resolution and DPI explainedResolution and DPI get used interchangeably and are not the same thing. What each actually means, why "300 DPI" alone tells you nothing, and how to work out what you need.
• Are online file converters safe?Most converters upload your file to a server you know nothing about. Here is what that means, what the privacy policies actually say, and how to check whether a tool needs to upload at all.