Compress an Image in the Browser: 82% Smaller, and When It Gets Bigger

I work on OnePassApps. We build browser studios that process files in the tab instead of uploading them, and this is the Image Studio's Compress tab.

If you have ever shrunk a photo to get under an upload limit, you have probably done it the uncomfortable way: pick a file, hand it to a website you do not control, wait for it to come back. For a passport scan, a medical record, a client deliverable, that upload is the part you cannot take back.

The Compress tab does the work in your own tab, and - this is the part worth checking - it shows you the before and after sizes instead of quietly claiming a win.

What the tab actually says

Open the Image Studio and the page line is plain: "Convert, compress, resize, crop and clean images in your browser. Nothing leaves this tab." The stage under the file repeats it: "Processing stays in this browser."

The Compress tab is laid out in three stages.

01 Source

No image yet. Drop one on the stage or browse for it.

The picker takes JPEG, PNG or WebP · up to 25 MiB and 25 megapixels.

02 Compression

Three output formats (PNG, JPEG and WebP), a quality slider, and one checkbox:

Shrinks larger images to fit, keeping the proportions.

That checkbox is Limit maximum dimensions. The quality slider runs from 10 to 100 and starts at 86. I did not switch it on for the runs below, so I am not going to guess what it does to the numbers - the panel's own line is above.

03 Result

The file sizes before and after appear here, so you can keep whichever copy is smaller.

Note the wording: whichever copy is smaller. The tool is not promising that the new file wins.

What actually came out

I ran it on a real 1400 × 1000 PNG - a gradient scene with a sun and film grain, 1.98 MiB - twice, changing one thing each time.

At the default quality of 86 the result panel read:

• Before: 1.98 MiB PNG
• After: 355.8 KiB JPEG
• Dimensions: 1400 × 1000
• 82% smaller, "Compressed in 0.3 s"

At quality 50 the same file came back as 110.3 KiB, 95% smaller, "Compressed in 0.4 s". The dimensions did not change in either run, because I left Limit maximum dimensions alone.

I checked the downloaded file rather than trusting the panel: the bytes start with the JPEG signature and the file is 364,342 bytes, which matches the 355.8 KiB the panel claims. The result card keeps the original next to the new copy and finishes with:

Finished. Download a new copy; the original stays unchanged.

The honest edge: it can get bigger

An earlier test of this same tab today, on a flat-colour PNG with no photographic detail in it, produced a copy that was 74.3% larger than the original - the tool said so itself, and still offered the original back.

That is not a failure, it is JPEG being honest: it spends bytes on detail, and a flat graphic has none to spend them on. Which is exactly why the result panel says "so you can keep whichever copy is smaller" instead of promising a smaller file every time. If your image is a screenshot or a logo, check the numbers before you take the new copy.

There is also no target-size box to type into. This tool compresses by format and quality and shows you the result, and you decide whether that result is good enough.

What it costs

The browser studios run on the OnePassApps membership. Standard is free right now at $0/month, with 100,000 credits every 30 days, no end date set and no card required, and no automatic paid subscription. You do not need an account to use the studios.

Try it on your own file: the Image Studio.

Every studio has a plain-language guide with the limits and the tool list: the OnePassApps guides.

I work on OnePassApps, so of course I am biased about these studios. What I tried to keep true here is the small set of facts you can check yourself: the accepted formats and limits, the slider range and its default, the two measured runs with their exact sizes and percentages, the JPEG bytes I read back, and the fact that the file is processed in your tab rather than uploaded.