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Base64 Image Encoder for Email

Convert images to base64-encoded data URIs for embedding directly in email HTML. Upload an image and get ready-to-use HTML, CSS, and raw base64 output.

About this tool

Base64 encoding lets you embed images directly in your email HTML without hosting them on a server. This can be useful for logos, icons, and small graphics that need to display immediately without external requests. However, base64 increases email size by roughly 33%, so use it sparingly and only for small images. For larger images, host them on a server and reference them with regular img tags. Check your total email size with our email word counter, and optimize your text-to-image ratio to maintain good deliverability.

Frequently Asked Questions

What is base64 encoding?

Base64 is a method of encoding binary data (like images) as ASCII text. It represents binary data using 64 printable characters (A-Z, a-z, 0-9, +, /). This allows you to embed image data directly in HTML or CSS without needing a separate file or server.

Which email clients support base64 images?

Gmail, Apple Mail, Thunderbird, Yahoo Mail, and most modern web-based email clients support base64 images. However, Outlook desktop (Windows) does NOT support base64 images and will show broken image icons. For maximum compatibility, host images on a server instead.

What is the maximum size for base64 images in emails?

Keep base64 images under 10KB for logos and icons, and under 50KB at the absolute maximum. Base64 encoding adds about 33% to the file size, so a 30KB image becomes roughly 40KB of text in your HTML. Large base64 strings can slow email rendering and trigger spam filters.

When should I use base64 vs hosted images?

Use base64 for small, critical images like logos (under 10KB) that must display immediately. Use hosted images for larger photos, banners, and product images. Hosted images load on demand and keep your email HTML lean, which improves deliverability.

Does base64 encoding affect email deliverability?

Yes. Large base64 strings dramatically increase your email HTML size, which can trigger spam filters. Many ESPs recommend keeping total email size under 100KB. A single large base64 image can easily exceed this. Stick to small images and check your total email size after encoding.

How do I use the generated base64 code?

Copy the HTML img tag output and paste it directly into your email HTML where you want the image to appear. The data URI contains the complete image, so no external hosting is needed. For CSS backgrounds, use the CSS background-image output in your inline styles.

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