LocalPixEmail clients and gateways often enforce attachment limits around 10–25 MB for the whole message (provider-dependent). A single full-resolution PNG screenshot can already be several megabytes; a short burst of them fails before you hit “Send.” The goal is a predictable file size, not a prettier palette.
What “compress for email” actually means here
LocalPix Compress to KB re-encodes the image as JPEG with a local quality search aimed at your target size. That is a size budget tool, not a lossless PNG optimizer. Transparency becomes a flat background once you leave PNG. If you must keep an alpha channel, stay on PNG and crop or downscale outside this tool — or accept that email-friendly delivery usually means JPEG or a smaller WebP that the recipient can open.
Pick a target before you open the tool
- ~100–200 KB — typical for a single screenshot in a short reply when you still want readable UI text.
- ~300–500 KB — safer when the shot has fine UI chrome or you are attaching two images under a tight mailbox quota.
- Under ~1 MB — usually enough headroom inside a 10 MB message that also carries other files; still verify your provider’s limit.
These are planning bands, not guarantees from any mail host. The tool’s number is the download size on your disk after encode.
Steps (local, 0-byte upload)
- Open Compress to KB. Leave DevTools Network open if you want to self-prove there is no photo upload.
- Drop a PNG, JPEG, or WebP from disk. Processing stays in the tab.
- Set Target KB (for example
150). Run Compress. - Check the preview: if UI text blurs, raise the target (e.g. 250–400) rather than sending an unreadable 80 KB file.
- Download the result (local
blob:URL). Attach that file in your mail client — not the original multi‑MB PNG.
PNG-specific pitfalls
- Screenshots with large flat areas often shrink well as JPEG; noisy photos need a higher KB budget for the same perceived sharpness.
- Already-small PNGs (icons, UI crops under ~50 KB) may not shrink further without obvious artifacts — skip recompression.
- Multiple attachments: budget the sum. Three “200 KB” shots are ~600 KB before the email MIME overhead.
- HEIC from a phone: convert first with HEIC to JPG, then compress if the JPEG is still over your limit.