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Image format guides
Simple answers to common image format questions. Written to answer the question rather than to fill a page.
18 guides
- HEIC
What is a HEIC file?
HEIC is the format iPhones shoot by default, at about half the size of JPEG. What it is, why Apple uses it, and what it does that JPEG cannot.
4 min read - HEIC
Why HEIC files won't open on Windows
Windows often cannot open HEIC because the HEVC codec it uses is patent-encumbered and no decoder ships by default. Three ways to fix it.
4 min read - HEIC
How to turn off HEIC on your iPhone
Turn off HEIC on iPhone: Settings, Camera, Formats, Most Compatible. Your phone shoots JPEG from then on. What it costs, and a better option.
3 min read - HEIC
HEIC vs JPEG — which should you keep?
HEIC files are half the size with better colour and more features. JPEG opens everywhere. Which matters depends entirely on where the photo is going.
3 min read - JPG
WebP vs AVIF vs JPEG, compared
AVIF gives the smallest files, WebP the best balance, JPEG the widest compatibility. Serve all three with a picture element and let the browser choose.
4 min read - HEIC
Why an upload form says your file is not an accepted image type
Upload forms reject HEIC, JFIF, WebP and AVIF because they only accept JPG and PNG. What the error means, why renaming fails, and how to fix it.
4 min read - JFIF
What is a JFIF file?
A JFIF file is a JPEG: same compression, same bytes, different extension, caused by a Windows registry setting. Why it happens and how to fix it.
4 min read - HEIC
How to convert HEIC to JPG on an iPhone
iOS can convert HEIC to JPG on its own — through the Shortcuts app, by pasting into Files, or automatically when you share. No third-party app required.
4 min read - HEIC
What image format do online forms accept?
JPG and PNG are accepted almost everywhere. What gets rejected, why size limits cause as many failures as formats, and what portals mean by KB limits.
4 min read - SVG
SVG vs PNG
SVG stores drawing instructions and scales to any size; PNG stores pixels and opens everywhere. Which to use for logos, icons, screenshots and photographs.
4 min read - WebP
What is a WebP file?
WebP is the format most of the web is served in. Why saving a picture from a website gives you one, and why your desktop software will not open it.
4 min read - HEIC
Does converting an image remove its EXIF data?
Converting in a browser discards EXIF entirely, GPS included. What your photos carry, why conversion strips it, and what survives each way of sharing.
6 min read - HEIC
Why your photo comes out sideways
A portrait photo that is upright on your phone and sideways everywhere else is not corrupted. The camera never rotated it — it wrote a flag instead.
5 min read - PNG
Why a transparent PNG turns black as a JPG
JPEG has no transparency, so every transparent pixel becomes a colour — usually black. Why it happens, and how to avoid the halo even when it is white.
5 min read - AVIF
What is an AVIF file?
AVIF is the newest web image format: about half the size of JPEG, royalty-free, supported by every current browser. Why almost nothing else reads it.
5 min read - HEIC
Why your converted image got bigger
Converting changes how an image is stored, not how much is in it. Why HEIC to JPG doubles the size, why PNG output is huge, and what actually helps.
5 min read - PNG
Why your screenshot is a huge PNG file
A screenshot is saved as PNG, which never throws anything away, and a high-DPI screen doubles the pixels. Why they are so big and how to shrink one.
5 min read - HEIC
Email attachment size limits, and how to get under them
Gmail allows 25 MB, the Outlook app 20 MB, and Exchange often 10 MB. Why the real limit is lower than the number, and how to get a photo under it.
4 min read
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