Compress to KB topic guide

Compress images for email: hit Gmail and Outlook attachment caps

Direct answer

Email attachment limits are message totals, not per-file wishes. Gmail Help states personal accounts allow 25 MB of attachments; Outlook.com’s sending-limits page sets the same 25 MB file attachment cap and notes that OneDrive links do not count toward that limit. When several photos push the message over the cap, Gmail may swap the files for a Drive link and Outlook may refuse the send. Compress the images to a deliberate KB/MB budget first if you need them to travel as real attachments.

Try the Compress to KB

What this workflow handles

Treat the published cap as a shared budget across every attached and inline file in that message. Gmail Help (support.google.com/mail/answer/6584) documents a 25 MB limit for personal Gmail and says Workspace admins set work/school limits — Google Workspace Help (support.google.com/a/answer/166852) lists Business and Education sending attachment limits at 25 MB, with Enterprise Plus up to 50 MB on web Gmail only. Microsoft’s Outlook.com sending-limits page states a 25 MB attachment size limit and a 2 GB OneDrive-linked file option; the Outlook.com “Unable to attach files” article adds that the 25 MB ceiling includes message text plus inserted and attached files, and that resizing an image’s display size does not reduce file bytes. Prefer JPEG for photographs when the recipient’s client may reject WebP. Use Compress to KB with a target safely under your remaining headroom (for example under 5000 KB per photo when you plan several images inside a 25 MB message).

Use Compress to KB to set a per-photo budget under your email’s remaining headroom. For format choice before you compress, read JPEG vs PNG vs WebP.

How to use it

  1. Open the sender’s official help page and note the published attachment cap (personal Gmail 25 MB; Outlook.com 25 MB; Workspace editions per admin / Workspace Help).
  2. Count every attached and inline file that will ride in the same message, leave headroom for the body text, and pick a per-image KB target under the remaining budget.
  3. Convert photographs to JPEG when clients may reject WebP; keep PNG for sharp graphics or required transparency.
  4. Upload each photo to Compress to KB, enter the per-image target, quality-sweep first, and downscale only if the quality floor still misses the budget.
  5. Re-sum the attachment bytes in the composer before send. If you still exceed the cap, drop a file, lower targets further, or switch that file to a Drive/OneDrive link per the platform docs.

Frequently asked questions

What is Gmail’s attachment size limit?

Gmail Help states that personal Gmail accounts have a 25 MB attachment limit. If the total attachment size exceeds that limit, Gmail removes the attachment and adds a Google Drive link instead. For work and school accounts, the Google Workspace administrator sets sending and receiving attachment limits — Workspace Help lists Business and Education at 25 MB sending, and Enterprise Plus up to 50 MB on web Gmail.

What is Outlook.com’s attachment size limit?

Microsoft’s Outlook.com sending-limits page states the file attachment size limit is 25 MB. You can also share a file from OneDrive; that article lists a 2 GB limit for OneDrive-linked files. The Outlook.com “Unable to attach files” article clarifies that the 25 MB email size limit includes all text, inserted images and attached files.

Does resizing an image in the email composer reduce the attachment size?

Not reliably. Microsoft’s Outlook.com attach troubleshooting page says resizing an image does not reduce its file size — you need to compress the file or attach a OneDrive link. Gmail can insert a Drive link automatically when the total exceeds 25 MB, which is a delivery change, not a smaller binary. Compress photos before compose when you need a real attachment under the published cap.

How should I pick a KB target for several photos in one email?

Start from the published message cap (25 MB on personal Gmail and Outlook.com), leave headroom for the message body and any other files, then divide the remaining budget across photos. Example: five photos inside a 25 MB message might each target under 4000–5000 KB so the sum stays comfortably under the cap. Enter that target in Compress to KB and re-check the sum before send.

JPEG, PNG or WebP for email photos?

Prefer JPEG for continuous-tone photographs when you need maximum client compatibility. PNG fits graphics or screenshots with sharp edges or transparency needs. Many email clients still handle JPEG and PNG more predictably than WebP; if a recipient’s client rejects WebP, the smaller WebP file never helps. Match the format to the content, then compress to the KB budget.

When should I use a Drive or OneDrive link instead of compressing?

When the file must stay original quality, is a video, or will still exceed the attachment cap after a reasonable quality sweep. Gmail Help documents automatic Drive linking above 25 MB; Outlook.com documents OneDrive sharing up to 2 GB for linked files. Compress when you need the bytes inside the message; use cloud links when fidelity or size makes that impossible.

How is this different from the general compress-to-KB guide?

The compress-image-to-kb guide covers hard byte budgets across forms, marketplaces and passport uploads (GOV.UK, LinkedIn, Shopify). This page isolates email attachment caps from Gmail Help and Outlook.com Support, including the shared-message budget and when platforms substitute cloud links. Same Compress to KB tool; different destination rules.

Sources

Explore the compress to kb topic cluster

This guide covers email attachment caps. Related guides cover general KB budgets, format choice, and balanced re-encode without a target.

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