What Image Size Should I Use for Online Forms?
A reference for the question every upload field eventually asks. Bookmark it; the numbers barely change.
Reading a size requirement correctly
Upload rules state up to three constraints, and they’re independent: file size (KB/MB — what storage costs), pixel dimensions (width×height — what layouts need), and format (JPG/PNG/PDF — what their software parses). “Under 100KB” says nothing about pixels; “1080×1080” says nothing about KB. Satisfy each one stated, ignore the ones that aren’t.
Application portals (the strict class)
- Photo fields: typically 20–50 KB, often 200×230px, JPG — 20KB / 50KB tools.
- Signature fields: 10–20 KB at ~140×60px — 10KB tool.
- Document scans: 100–300 KB per page, frequently as PDF — JPG→PDF under 100KB.
- Watch for minimums: “20KB–50KB” rejects too-small files too — increase tool.
Profiles and avatars
- Professional networks: 400×400px square, generous KB allowance — LinkedIn tool.
- General avatars: 200–800px square; 100–200 KB keeps every system happy — 100KB tool.
- Older forums/intranets: often hard-capped at 100 KB or below.
Social platforms
- YouTube thumbnail: 1280×720, under 2MB — tool.
- Instagram post: 1080×1080 — tool; story/Reels/TikTok/Shorts: 1080×1920 — tool.
- X/Twitter header: 1500×500; Facebook cover: 820×312 — both via by-pixels.
Email and documents
- Attachments: 500 KB–1 MB per image keeps any message deliverable — 500KB / 1MB.
- PDFs for upload: portals cluster at 100/200/500 KB caps — PDF tools.
When the form doesn’t say
No stated limit? Use the destination as the guide: 100–200 KB for anything profile-like, 300–500 KB for content images, 1 MB for email. If an unstated limit rejects you anyway, the error usually names it — then it’s one pass through the exact-KB tool with that number.