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Image size requirements for email and online stores

Most rejected images come down to three numbers: pixel dimensions, file size and file format. This guide collects the official limits of the main email services and online marketplaces, and the order of steps that gets an image accepted the first time.

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Three different limits

  • Pixel dimensions (for example 2048 × 2048 px) decide how sharp the image looks and whether zoom works. You change them by resizing.
  • File size (for example 20 MB) decides whether the upload is accepted and how fast the image loads. You reduce it by compressing.
  • File format (JPG, PNG, WebP and so on) must be one the platform accepts. You change it by converting.

Bitinz handles the second and the third: it compresses JPG, PNG and WebP files and converts JPG and PNG to WebP. It does not resize, so set the dimensions first in your photo editor.

Email attachments

ServiceAttachment limitWhen files are larger
Gmail (personal accounts)25 MBGmail replaces the attachment with a Google Drive link
Outlook.com25 MBShare the file from OneDrive instead (up to 2 GB)
Classic Outlook (POP and IMAP accounts)20 MB by defaultOutlook shows an error and does not send the message
iCloud Mail20 MB per messageMail Drop sends files up to 5 GB as a link
Yahoo Mail25 MB in totalSend a link to the file in cloud storage instead

Two details catch people out. The limit applies to all attachments in a message together, so five photos of 6 MB each will not fit under 25 MB. And attachments are encoded for sending, which makes them roughly a third larger on the way (Microsoft documents about 33%), so a message right at the limit can still be rejected. Leave some room.

Compressing photos before attaching them often brings a batch back under the limit without changing their dimensions. For many large files, a shared link is the better choice.

Compress imagesMake JPG, PNG and WebP files smaller in their own format, in batches and for free.Compress images

Images inside newsletters

Email layouts are narrow. Mailchimp designs its templates for a maximum width of 600 pixels, so an image about 1200 pixels wide stays sharp on high-density screens. Mailchimp recommends keeping each image under 1 MB, and accepts JPG, GIF and PNG.

Email apps do not all display WebP, so use JPG for photos and PNG for logos in emails, compressed in their own format. Heavy images make an email slow to open, especially on a phone.

Online stores and marketplaces

PlatformRecommended sizeLimitsFormats
Shopify2048 × 2048 px for square imagesUp to 5000 × 5000 px, under 20 MBPNG, JPG, WebP, GIF, HEIC and more
Amazon1000 px or more on the longest side, which enables zoom500 to 10,000 px on the longest sideJPG (preferred), PNG, TIFF, GIF; no WebP
EtsyAt least 2000 px wide and highFirst photo at least 635 px; files over 1 MB may fail on slow connectionsJPG, PNG, GIF, SVG, HEIC; no WebP
eBayAbout 1600 × 1600 pxAt least 500 px, up to 12 MBJPG, PNG, WebP, AVIF, HEIC and more

Larger is not always better: a photo far beyond the recommended size takes longer to upload and gains nothing once the platform shrinks it for display. Aim for the recommended size, then compress.

Rules beyond size

  • Amazon: the main image needs a pure white background (RGB 255, 255, 255), with the product filling about 85% of the frame. Amazon also asks for images with minimal compression, so upload high-quality originals and compress only a file that is too large to upload, then check it at full size.
  • Etsy: animated GIFs and transparent PNGs are not supported, and Etsy converts images to the sRGB colour space.
  • eBay: up to 24 photos per listing, with no borders, watermarks or added text.
  • Shopify: PNG and JPG are the recommended formats for product photos; keeping square photos at one size makes collection pages line up neatly.

A workflow that passes the first time

  1. Look up the platform's current requirements: the tables above, or the official pages listed below.
  2. Resize the image in your editor to the recommended dimensions, not larger.
  3. Keep a format the platform accepts: JPG for photos, PNG for graphics. Use WebP only where it is listed.
  4. Compress with Bitinz, keeping the format, and compare the result with the original.
  5. Check the file sizes against the limit, leaving some room for email.

For your own website, you set the rules: see how to compress images for a website and JPG, PNG or WebP: which to use.

Tools in this guide

Sources

Figures checked against the official pages on October 22, 2026. Platforms change their rules, so check the linked page before relying on a limit.

  1. Google: Gmail Help: Attachment size limits
  2. Microsoft: Sending limits in Outlook.com
  3. Microsoft: Attachment size exceeds the allowable limit (classic Outlook)
  4. Microsoft: Exchange Online limits
  5. Apple: iCloud Mail storage and message limits
  6. Yahoo: Attachment size limits in Yahoo Mail
  7. Mailchimp: About template images
  8. Shopify: Product media types
  9. Amazon: Product image guide
  10. Amazon: Technical image file requirements
  11. Etsy: Requirements and best practices for images
  12. eBay: Adding pictures to your listings
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