swiftimg

Image hosting for newsletters — Substack, Buttondown, Mailchimp

Email clients fetch images by URL when the recipient opens the message. swiftimg gives you a stable, globally cached URL you can drop into Substack, Buttondown, Mailchimp, or a plain Markdown newsletter.

Try swiftimg freeSee the API

Heads-up

Many email clients block remote images by default until the reader opts in. That's a client behaviour, not a hosting issue — any image host has the same caveat.

Step by step

  1. 1. Upload the hero image

    Drop it at /upload. Anonymous uploads work, but signing in lets you keep a library of newsletter assets you can reuse.

  2. 2. Paste the URL into your newsletter editor

    Substack, Buttondown, Mailchimp, and ConvertKit all accept external image URLs in their editors and inline an <img src=…> for you.

  3. 3. Pre-size for retina

    Generate a 2× width variant for retina screens and let the email client downscale.

    Pre-sized retina variant
    https://i.swiftimg.com/abc123.png?w=1200&fm=webp&sig=...

Email newsletters — FAQ

Does swiftimg work as an SMTP / sending provider?

No — it only hosts the images. Use your existing newsletter tool to send; just embed the swiftimg URL.

Will the link still work in archived issues?

Yes. Uploads don't expire, so a newsletter you sent years ago keeps rendering its images.

Should I use WebP in emails?

WebP is supported in Apple Mail, Gmail, and modern Outlook; older clients fall back. If you want maximum reach, serve PNG/JPEG and let swiftimg deliver from its global cache.

See also

Ready to host your Email newsletters images?

Start free, then unlock the full API, transforms, signed URLs, and a custom domain on the Developer plan.