Government portals, job applications, exam registrations and older CMS uploads routinely cap files at 100 KB, 200 KB or 500 KB. A modern phone photo is 3–8 MB, so you need a 30–80× reduction.
Cranking the quality slider alone will get you there and make the image look terrible. Do these three things in order instead.
Step 1: Resize before you compress
This is the step people skip, and it does most of the work.
File size scales with pixel count, which scales with the *square* of the dimensions. Halving width and height quarters the pixels — and roughly quarters the file size — before any quality loss.
A 4000 × 3000 photo is 12 megapixels. If the destination displays it at 800 × 600, those extra pixels are discarded on upload anyway. You are spending your entire byte budget on detail nobody sees.
Sensible targets:
| Use | Dimensions | Realistic size |
|---|---|---|
| Passport/ID photo upload | 600 × 800 | 30–60 KB |
| Profile picture | 400 × 400 | 20–40 KB |
| Document scan | 1240 × 1754 (A4 @150dpi) | 80–150 KB |
| Web content image | 1200 wide | 100–200 KB |
Resize first with the image resizer, then compress. Doing it the other way round wastes quality — you compress detail, then throw the pixels away.
Step 2: Pick the right format
Format choice can halve the size on its own, and the right answer depends on what is in the picture.
| Content | Best format | Why |
|---|---|---|
| Photograph | JPEG or WebP | Handles smooth gradients efficiently |
| Screenshot, text, line art | PNG or WebP | Sharp edges survive; JPEG smears them |
| Needs transparency | PNG or WebP | JPEG has no alpha channel |
| Anywhere modern browsers only | WebP | Typically 25–35% smaller than JPEG |
WebP is the default choice now — it is supported by every current browser and consistently beats JPEG at equal visual quality. The exception is upload forms that only accept JPG or PNG, which is common on older government portals. Check what is accepted before converting.
The image converter handles JPG, PNG and WebP in both directions.
One thing worth knowing: converting a JPEG to PNG will usually make it *larger*, not smaller. PNG is lossless, so it faithfully preserves the JPEG's compression artefacts at full cost. Only go to PNG if you need transparency or the content is graphics rather than photography.
Step 3: Compress, and know what the slider does
JPEG quality is not a percentage of anything meaningful. It controls how aggressively frequency detail is discarded, and the relationship to file size is very non-linear:
| Quality | Relative size | Visible result |
|---|---|---|
| 100 | 100% | Wasteful — nearly indistinguishable from 90 |
| 90 | ~45% | Excellent, no visible artefacts |
| 80 | ~30% | The sweet spot for most photos |
| 70 | ~23% | Slight softening in fine detail |
| 60 | ~19% | Visible artefacts around edges |
| 40 | ~14% | Obvious blocking |
The jump from 100 to 90 halves the size for essentially no perceptible loss. From 80 to 70 saves comparatively little and costs more. Start at 80 and adjust only if you are still over the limit.
Use the image compressor to apply this, and check the resulting file size before uploading.
Putting it together
For a 6 MB phone photo that must fit in 100 KB:
1. Resize to 800 × 600. That alone typically lands you around 400–600 KB. 2. Convert to JPEG if it is a HEIC or PNG, or WebP if the form accepts it. 3. Compress at quality 80. Usually 60–90 KB. 4. If still over, drop to quality 70 before resizing further. Below 640 px wide, text in document scans starts becoming unreadable.
Common mistakes
- Compressing an already-compressed JPEG repeatedly. Every save re-encodes and loses more. Always start from the original, never from a file you have already squeezed.
- Screenshotting instead of resizing. A screenshot of an image adds your screen's scaling artefacts on top of the original's.
- Using PNG for photographs. Frequently 5–10× larger than an equivalent JPEG with no visible benefit.
- Ignoring EXIF data. Camera metadata can add 20–50 KB, and includes GPS coordinates. Stripping it saves space *and* removes the location of where the photo was taken — worth doing before any public upload.
- Assuming the limit is in KB not KiB. Some systems mean 100,000 bytes, others 102,400. Leave a few percent of headroom.
Frequently asked questions
Can I compress without any quality loss?
Only with lossless formats (PNG, lossless WebP) and the savings are modest — typically 5–20%. Hitting 100 KB from a phone photo requires lossy compression.
Why is my PNG screenshot so large?
PNG stores every pixel exactly. Screenshots with photographs or gradients in them compress poorly. Crop to just the region you need, or convert to WebP.
Does resizing lose quality?
Downscaling discards pixels, but if the display size is smaller than the original you lose nothing visible. Upscaling never adds real detail.
Are these tools private?
The resizer, converter and compressor all run in your browser — the file is not uploaded anywhere. That matters for ID documents.
What about HEIC from an iPhone?
Convert it first; most upload forms reject HEIC outright. See [HEIC to JPG](/blog/heic-to-jpg-windows-android).
Related reading
If your source is an iPhone photo, start with converting HEIC to JPG. For dimension changes, the image resizer works by pixels or percentage.