Image Compression FAQ: 15 Common Questions, Answered

The Basics

Q: Does compressing an image always reduce its quality?

Not always. Lossless compression (used by PNG) makes files smaller without changing a single pixel. Lossy compression (used by JPEG and WebP) does discard some data, but at sensible quality settings — roughly 75 to 85 — the loss is invisible to the eye while the file gets dramatically smaller. "Compressed" and "worse-looking" are only the same thing when you push the quality too low.

Q: What's the difference between lossy and lossless compression?

Lossless preserves every pixel exactly; decompressing gives back the original. Lossy permanently removes information judged least visible to humans, trading a little fidelity for a much smaller file. Use lossless (PNG) for screenshots, logos, and graphics with text. Use lossy (JPEG/WebP) for photographs. See how image compression works for the full mechanics.

Q: Can I get quality back after compressing?

No, not for lossy formats. Once JPEG or WebP discards data, it's gone — re-saving at a higher quality number doesn't recover it, it just makes a bigger file from the already-degraded image. Always keep your original. Compress copies, never your masters.

Formats

Q: Which format gives the smallest file?

For photographs, WebP usually wins — typically 25–30% smaller than JPEG at the same visual quality. For graphics with flat color and text, lossless WebP or PNG is best. There's no single answer; it depends on the image. The honest move is to try two formats and compare. See JPEG vs PNG vs WebP.

Q: Is WebP supported everywhere now?

In browsers, effectively yes — every current browser has supported WebP since 2020. The gaps are outside the browser: some older image editors, a few email clients, and certain older systems still don't read it. For the web, WebP is a safe default. For email or sending a single file to someone, JPEG is safer — see reducing image size for email.

Q: Should I convert all my JPEGs to WebP?

For images on a website, serve WebP with a JPEG fallback using the `<picture>` element — the browser picks the best supported format and you save bandwidth. For images stored locally or emailed, keep JPEG, because the recipient's tool might not read WebP.

Q: What is MozJPEG, and is it different from regular JPEG?

MozJPEG is a JPEG encoder tuned to produce smaller files at the same visual quality — usually around 10% smaller than a standard JPEG. The output is still an ordinary .jpg that opens in any viewer; only the encoding is smarter. See MozJPEG vs standard JPEG.

Quality and Settings

Q: What quality setting should I use?

For most photographs, 75 to 85 is the sweet spot: visually indistinguishable from the original at a fraction of the size. Below 60, artifacts become obvious. Above 90, files grow quickly with no visible gain because the encoder is preserving detail your eye can't see.

Q: Why does my image look blocky after compression?

That's over-compression — the quality was set too low, so JPEG's 8×8 processing blocks become visible, especially in smooth areas like skies and gradients. Raise the quality setting. If it only happens around text or sharp edges, the real fix is using PNG for that image instead of a lossy format.

Q: Does resizing an image also compress it?

Resizing and compression are different but complementary. Resizing reduces the pixel dimensions; compression reduces the bytes needed to store those pixels. Doing both is the most effective approach: shrink a 4000 px image to the size it's actually displayed at, then compress. Resizing first removes most of the weight before the encoder even runs.

Practical Concerns

Q: Will compressing remove my EXIF and location data?

It often does, and that's frequently a good thing — EXIF can contain GPS coordinates and camera details you may not want to publish. Many compressors strip this metadata by default, which also shaves a little off the file size. If you need EXIF preserved (for photography portfolios, say), check that your tool keeps it.

Q: Is it safe to compress images in my browser?

With a tool that runs entirely client-side, yes — and it's more private than the alternative. TinImg processes images locally using WebAssembly, so files never upload to any server. Tools that require an upload do see your files, which matters for anything sensitive.

Q: Can I compress transparent PNGs without losing transparency?

Yes. Keep them as PNG, or convert to WebP, which supports transparency at a much smaller size than PNG. The one thing you can't do is convert a transparent image to JPEG — JPEG has no transparency channel, so transparent areas become solid (usually white or black).

Q: How small can I make an image without it looking bad?

It depends entirely on the image. A simple graphic with flat colors can shrink enormously. A detailed photograph with fine texture has a lower floor before artifacts show. Rather than chasing a target file size, set a quality level you're happy with and accept whatever size that produces — the result looks consistent across images, which a fixed size target won't.

Q: Why is my PNG bigger than the JPEG version of the same image?

Because PNG is lossless and the image is probably a photograph. PNG keeps every micro-variation in every pixel, which is wasteful on photographic content — a photo saved as PNG is commonly five to ten times larger than the JPEG. PNG only wins on flat graphics, logos, and images with sharp text.