画像をBase64に変換

This image to Base64 converter turns a picture into a data URI, a long text string that embeds the image directly, plus a ready-to-use CSS background snippet. You can inline an image instead of linking to a separate file.

It runs locally in your browser, so your image is read on your device and never uploaded.

A data URI carries the whole image inside the markup, so the browser does not make a separate network request to fetch it. For small assets like icons, that saved round trip can make a page feel faster.

The catch is size and caching. Base64 adds roughly 33 percent overhead because it represents binary data with a limited text alphabet, and an inlined image cannot be cached separately, so it is downloaded again with every page that contains it.

The rule of thumb is to inline small images, icons, tiny logos or a sprite, where avoiding a request is worth the overhead, and to keep larger images as normal files that the browser can cache and load in parallel.

Data URIs work anywhere a URL is accepted: an img src, a CSS background, or a field in JSON or an email template. That makes them handy for self-contained snippets.