The short answer
Two steps. First, bring the long edge down to roughly 1200 pixels. Second, enable "compress to target size", enter 200 (KB), and pick WebP — the tool walks the quality back automatically until it fits. Most phone photos land at 150–200 KB this way with faces and text edges intact. If the system only accepts JPG, switch to JPEG at quality 80 and step down by 5 until it fits. Resize first, then quality — the order matters, and the maths below shows why.
Where the 200 KB caps come from
The classic case is exam registration: teaching certificates, civil-service exams, CET-4/6 and Mandarin tests typically ask for "JPG, 20–200 KB, one- or two-inch". Then come CV attachments, visa and ID uploads, bid documents, and any web form that says "attachment no larger than X MB". What they share is that the system checks a single number — the file size — and will not make exceptions for clarity. So the strategy is purely mechanical: get inside the limit while sacrificing as little perceived quality as possible.
Do not "compress" via WeChat
A popular trick: send the photo to yourself in a chat app and save it back — the file shrinks. It works, but not for anything that matters. The compression strength is uncontrolled and the image gets re-encoded, so faces can turn muddy and edges soft — exactly what a photo reviewer is told to reject. Chat compression is tuned for preview thumbnails, not for "just under 200 KB and as sharp as possible". Compress it yourself and you control every parameter.
The two-step routine
Step one, set the dimensions. Exam photos usually specify a size: 295×413 px for one-inch, 413×579 px for two-inch — crop to proportion first. For photos without a stated size, a 1200 px long edge is plenty (far sharper than any phone screen needs). Step two, hit the size. Open the image compressor, tick "compress to target size", enter 200 KB, choose WebP — the tool adjusts quality automatically. If the system demands JPG, choose JPEG at quality 80 and drop by 5 each pass; one or two rounds is typical.
Why resizing must come first
The arithmetic settles it. A 4000×3000 phone original is about 6 MB; at 1200×900 only 9% of the pixels remain — that step alone usually lands the file under 1 MB with no visible change on screen. At 80% quality it slips under 200 KB easily. Run it the other way — keep 4000×3000 and crush quality to 30% — and you get colour fringing around text, blocking in dark areas, and you still may not fit inside 200 KB. Same target: one path is nearly lossless, the other is blurry and unreliable. The order is everything.
Cheat sheet: target size to settings
Skip the trial and error: for a 200 KB target, long edge 1200 px at JPEG quality 80 is a safe start. For 100 KB, use 1000 px at 75. For 50 KB, 800 px at 70. For a demanding 20 KB cap, use 600 px at 70 — or crop to the one-inch spec of 295×413 directly. These are experience values for ordinary phone photos; very detailed or noisy night shots run slightly larger, in which case the target-size mode converges automatically.
Three checks after compressing
First, look: zoom in on text edges and faces — for exam photos, the facial outline is what reviewers check. Second, the number: confirm the actual file size in its properties, not just the tool's estimate. Third, the format: make sure the extension matches what the system demands — renaming .png to .jpg is not conversion, the file will still fail to open; run it through a real converter. For IDs and contracts, strip the EXIF afterwards so the shooting location does not travel with the file.
想马上动手：用 图片压缩 的「目标大小」模式压一张，尺寸不合适先去 批量改尺寸，证件规格用 图片裁剪 按比例裁。Try it now: hit your target size with the image compressor, resize first with the batch resizer, and crop to ID proportions with the cropper.
FAQ
The file is under 200 KB but the reviewer says it looks blurry. Now what?
The resolution was probably cut too hard. Raise the long edge back to 1600 and let the target-size mode converge automatically — more pixels means less quality headroom, but reviewers judge overall sharpness, not noise at 300% zoom. If the system forces JPG, prefer dropping one size step over letting quality fall below 75.
Converting PNG to JPG turned the background white and the transparency vanished.
JPG has no alpha channel, so transparent areas are always filled — white by default. If you need transparency, keep PNG and use the target-size mode on PNG instead. If the system asks for JPG anyway, a white background is the expected result; just check the edges are clean.
Can I put dozens of photos under 200 KB in one go?
Yes. Batch-resize every photo to a 1200 px long edge first, then drop the whole batch into the compressor with "target size 200 KB" ticked and download as ZIP. Note that target-size works per image: final sizes hover just under 200 KB but none of them exceed it.