How do I embed an image in an email?
Either attach the image and paste it into the email body (most clients inline it), or use an <img src='URL'> tag pointing to a hosted image. For marketing emails and HTML newsletters, the URL approach keeps the email small and consistent across clients.
Email supports two embedding mechanisms. The first is a multipart MIME attachment referenced via cid: — the image lives inside the email itself. The second is an external <img> tag that fetches the image from a remote URL when the recipient opens the email. Which one to use depends on your audience and delivery pipeline.
For casual one-off emails from Gmail or Outlook, just drag the image into the message body. The client handles the MIME attachment automatically. Pros: no external dependency, works even if the recipient has images-blocked. Cons: the email is larger, and some spam filters flag large inline images.
For marketing emails, newsletters, and transactional emails sent from Mailchimp, SendGrid, Postmark, or Resend — use hosted URLs. The email stays lightweight (maybe 20 KB), and you can update the image at the host without re-sending the email. Use a fast, global CDN so subscribers everywhere get fast load times.
For corporate signatures (the logo at the bottom of your replies), use a hosted URL. A linked signature image is 0 bytes in each email; an inline one adds 5–20 KB to every send. Over a year of emails, that's a meaningful amount of bandwidth you're attaching to everything.
Gmail proxies external images through a Google-controlled domain for privacy, which means your host has to return an Access-Control-Allow-Origin header and accept Google's crawler. Hosts like ImageToURL set these correctly; some amateur hosts don't, which shows the 'image could not be loaded' placeholder in Gmail.
Related questions
Why doesn't my email image show up for some recipients?
Most email clients block external images by default for privacy. Recipients need to click 'Show images' once per sender. To force inline rendering, use MIME attachment with cid: reference — works even with images blocked.
What size should my email images be?
Max 600px wide for most clients (Gmail caps rendered width around there). File size: under 200 KB per image for fast open times. Use a WebP/JPG at quality 80 via the image compressor before hosting.
Does Apple Mail / Outlook handle external URLs differently?
Apple Mail fetches external images directly from your host unless Mail Privacy Protection is on (then it pre-loads via Apple proxy). Outlook 365 caches images in its image proxy. Use a fast CDN to avoid the pre-load delay showing blanks.
Can I track who opens the email via the image URL?
Yes — some platforms use a tiny tracking pixel (1×1 image) with a unique URL per recipient. Most marketing tools (Mailchimp, SendGrid) do this automatically. Image hosts can log per-URL access; ImageToURL offers this on Pro.
Does embedding an image affect email deliverability?
Yes. Poorly-optimized images (too large, slow host, high image-to-text ratio) can trigger spam filters. Keep the image-to-text ratio balanced and make sure alt text is set on every <img> tag.
Why does my logo look pixelated in email?
Most clients have retina-display support — serve 2× resolution in the source and display with width/height attributes. E.g., 400×120 logo served as 800×240 PNG with width='400' height='120'.
Can I use SVG in email?
Spotty support. Gmail renders SVG, Outlook 365 doesn't consistently, Apple Mail does. Safer to rasterize to PNG via the image resizer before email.
How do I embed an animated GIF?
Gmail and Apple Mail play them. Outlook shows only the first frame. Make sure frame 1 carries the key message for Outlook users.