How to Convert an Image Format Without Making It Bigger

Converting an image is the decision most people skip and then regret. Squeezing a photograph harder trades away detail you can see; moving it to a format built for photographs can halve the file with nothing visibly lost. This is the whole tool explained, with the numbers we measured rather than the ones we assumed — including the conversions that make your file four times bigger, and how the screen warns you first.

Open the Convert Image tool — free, no sign-up, no watermark.

What converting actually does

The picture is decoded to raw pixels and encoded again by a different set of rules. That is why the same photograph can weigh 187 KB as a JPEG and 1.09 MB as a PNG without a single pixel changing.

Formats are not better or worse in the abstract; they are specialised. JPEG and its successors were built for photographs, where colour varies continuously and small errors hide in the noise. PNG and GIF were built for flat artwork, where colour comes in large uniform areas and one wrong pixel on a hard edge is obvious. Choose against the grain of your image and the file balloons.

So the useful question is never "which format is smallest" but "what kind of picture is this". Converting is different from compressing, which keeps the format and spends fewer bytes describing the same pixels, and from resizing, which changes the pixel count. Pixpoo keeps the first two apart on purpose: Compress Image never changes your format, so the two decisions stay separate.

Step 1: add your image

Drag a file in, or click to browse. The tool reads it off disk, measures it, and reports which of those is happening rather than running on a timer.

Accepted formats are JPG, PNG, WebP, AVIF, GIF and TIFF, up to 25 MB. iPhone HEIC files are refused — set Settings → Camera → Formats to Most Compatible first.

Step 2: convert options

The screen asks you for one thing: the format, as a row of tiles with your current one marked. A Quick Start row sits under it for the common jobs, an estimate sits below that so you can see what the choice costs, and everything else is folded into More options — because a conversion with the defaults left alone is the right answer most of the time.

Quick Start

Touching any control afterwards clears the chip, because the settings are no longer the ones it stands for. Two of the six behave differently from the rest: Max quality and Smallest change only the quality settings and leave whatever format you already chose in place.

Output Format

The answer flips completely depending on what the picture contains. Converting a 573 KB photograph at quality 80:

Photographs want JPEG, WebP or AVIF. Screenshots, logos and line art want PNG. WebP is the one format that is respectable at both.

AVIF deserves a note, because its ranking is not stable: at quality 80 it was the largest of the four sensible choices, but at quality 50 it produced 21 KB against JPEG's 43 KB. It wins precisely when you are compressing hard, which is the opposite of what "smallest format" usually implies.

Quality and compression, in More options

Both live inside More options rather than on the main screen: 82 suits almost every conversion, and the shortcuts above move it for the ones it does not. Quality disappears for GIF, which has no quality dial, and when you choose lossless, which has nothing to trade.

Leave it near the default for photographs. It is worth knowing that dropping the quality often does less for you than changing the format: on our test photo, moving from JPEG to AVIF at quality 50 saved more than halving the quality within JPEG did.

Compression

Lossy for photographs. Lossless when converting a logo, a diagram or a screenshot, where a softened edge is the thing people notice. We checked the promise rather than assuming it: decoding lossless WebP, PNG and AVIF output and comparing against the source, all three came back with identical pixels, every sample matching.

It is not cheap. On a 1000×1000 test crop, WebP came to 54 KB lossy and 967 KB lossless — which is why photographs belong on the other setting.

The estimate

It is arithmetic rather than a trial encode — running the real thing on every click would mean a round trip per press — so treat it as the shape of the answer. The download screen afterwards carries the real figure.

When the new file would be bigger

Choosing a format that stores your kind of picture badly is not blocked, but it is called out — the badge turns red and reads Larger than the original instead of Ready to Convert, and the size itself turns red with it. GIF additionally has no quality control at all, so the slider is replaced by a line saying so.

Converting a photograph to GIF took our 573 KB file to 2.41 MB, because GIF reduces the picture to 256 colours and then stores it in a way built for flat artwork. PNG did the same thing less dramatically at 1.09 MB. Both are the right choice for a logo and the wrong one for a photograph.

Transparency and background

Keep transparency carries an alpha channel into PNG, WebP, AVIF or GIF. JPEG and TIFF have no alpha channel, so anything transparent has to become a colour — the swatch row appears to let you choose white, black or your own, rather than being given white silently.

More options

Beyond quality and compression, three of these deserve a word.

Resolution (DPI) is metadata only — it changes no pixels and only print software reads it — and it has a consequence that is easy to miss. The underlying image library can attach a DPI only by writing the whole original metadata block back out, so choosing any value here restores the camera and location tags even with the metadata box ticked. We measured exactly that: 244 bytes of EXIF removed on the default path, and present again as soon as a DPI was set. If privacy matters more than the DPI figure, leave it on Keep as-is.

PNG effort is nearly free to ignore. Going from Fast to Maximum saved 0.4% on a photograph and 5% on a flat graphic, for up to twelve times the encoding time.

There is deliberately no resize here. Resize Image does that job properly — three ways of asking for a size, a live scale readout — and the finished screen hands your converted file straight to it. When the destination has a size rule as well as a format rule, do the two in sequence: it costs one press and no second upload.

Step 3: download

Change Format goes back to the options with the same picture still loaded, so trying a different format costs nothing. Convert Another clears it for a new file. The tiles below pass the finished image to Resize, Crop, Compress, Upscale or Watermark.

Where the honest edges are

Converting is a decode and a re-encode, so anything but a lossless destination costs a little detail — and converting a JPEG to PNG does not recover what the JPEG already discarded, it only stores the damage in a bigger file.

Choosing a format against the grain of your picture makes it heavier, sometimes several times over. Neither JPEG nor TIFF can hold transparency. GIF has no quality setting, and an animated GIF is flattened to a single frame. A TIFF result cannot be previewed on the download screen either — browsers cannot draw TIFF in a page, so the card explains that instead of showing a broken image. The downloaded file is correct. Setting a DPI restores the metadata the tool otherwise strips.

JPEG 2000 and JPEG XL are reachable over the API but are not offered on this screen, because both need optional libraries that a standard server build does not carry — offering a card that might fail is worse than not offering it. Dimensions are never changed here — a conversion converts and nothing else. Pictures go through one at a time, the upload ceiling is 25 MB, and conversion happens on a server, so the file does travel — it is processed and returned straight away, never written to disk and never shared.

Common questions

Which image format should I convert to?

For photographs going on a web page, WebP is the best default — smaller than JPEG at the same quality and supported everywhere that matters. For photographs that must open in old software, JPEG. For screenshots, logos, charts and anything with hard edges or transparency, PNG. For print, TIFF. AVIF is the smallest of all when you are compressing hard, though at gentle settings it can be larger than JPEG. GIF is for flat artwork with very few colours and almost never right for a photograph.

Does converting an image reduce its file size?

It can do more for the size than compressing does, or it can make things dramatically worse — the format has to suit the picture. Converting a 573 KB photograph at quality 80, we measured 187 KB as JPEG and 213 KB as WebP, but 1.09 MB as PNG and 2.41 MB as GIF. The estimate panel tells you which way it is going before you press anything.

Does converting reduce image quality?

Any lossy destination discards a little detail, and it stacks on top of whatever an earlier save already threw away. If you need the pixels intact, convert to WebP, PNG or AVIF and switch Compression type to Lossless; we decoded all three and compared them against the source, and every sample matched.

Will my transparent background survive?

Into PNG, WebP, AVIF or GIF, yes — Keep transparency is on by default. Into JPEG or TIFF, no: neither has an alpha channel, so transparent areas are filled with a colour you choose.

Can I convert a JPG to PNG without losing quality?

You can convert it without losing anything further — choose PNG and set Compression type to Lossless, and every pixel of the JPEG is preserved exactly. What you cannot do is get back the detail the original JPEG discarded when it was first saved. The result is a faithful, and considerably larger, copy of the JPEG as it stands.

Does converting remove EXIF and GPS data?

Yes by default. The one exception that matters: setting a Resolution (DPI) restores the whole metadata block, because the image library can only attach a DPI by writing the original metadata back out. We measured it — 244 bytes of EXIF removed on the default path, present again as soon as a DPI was set. If you care about privacy, leave Resolution on Keep as-is.

What is the difference between converting and compressing?

Compressing keeps the format and spends fewer bytes describing the same pixels. Converting changes the format, which changes the rules used to describe them. Converting is frequently the bigger win — moving a photograph to a format built for photographs can beat squeezing it harder in a format that is not.

Can I convert an animated GIF?

Not with the animation intact — the picture is read as a single frame, so what you get back is a still image.

Does converting change the image dimensions?

No. A conversion changes the file format and nothing about the pixel grid, so the download comes back at exactly the size it went in at. If you want a size change too, use Resize Image — the finished screen hands the converted file straight to it.

Does it work on a phone?

Yes. It runs in any modern browser on Android and iOS with nothing to install.

Try the Convert Image tool, or browse the rest of the Image Toolkit.