How to convert a HEIC to Base64 on a Mac

HEIC is what photographs from an iPhone are, unless someone changed a setting. It packs better than JPEG at the same quality, which is why Apple adopted it, and it is understood natively across macOS. Encoding one to Base64 works exactly as any other image does.

This guide covers encoding a HEIC in B64, and the compatibility question that matters at the far end.

Encode a HEIC

1. Open Encode

   Click Encode in the sidebar or press ⌘1.

2. Load the photo

   Drag it from the Finder onto the Encode area, click Choose File… (⌘O), or press ⇧⌘V to encode a copy already on your clipboard.

   .heic and .heif are both accepted, and a Live Photo's still image encodes like any other HEIC.

3. Pick the output format

   The data URI produced carries image/heic as its MIME type, which is the accurate declaration for these bytes.

4. Copy or export

   Copy (⇧⌘C) or Export… (⌘E).

The compatibility question

Base64 is a faithful representation of whatever file you give it, and this is the case where that cuts both ways. A HEIC encoded to Base64 is still a HEIC. It decodes perfectly — in this app, in Preview, anywhere macOS is doing the reading — but a consumer that does not understand HEIC will not render it just because it arrived as a data URI.

Where a HEIC payload is entirely sensible: anywhere macOS or iOS is at both ends, an archive or a transfer format, a field in your own application, or a case where you specifically want the original file preserved byte for byte rather than a converted copy of it.

What is preserved

Everything. HEIC files carry a great deal — the main image, often a thumbnail, depth data on portraits, EXIF including location, and the colour profile. All of it is in the bytes, so all of it is in the Base64 and comes back on decode.

That thoroughness is worth a thought before embedding one publicly: a HEIC straight from a phone can carry GPS coordinates and a great deal of camera detail.

Checking what you produced

Paste the result into Decode — free, and instant. It reports the format as HEIC, shows the dimensions, and renders the picture. If you expected a JPEG and get HEIC, you have caught the problem before it reached anything that cares.

The Inspector (⌥⌘I) also shows the declared and actual types, and a SHA-256 of the decoded bytes you can compare with the source.

Copying and exporting the result

Copy (⇧⌘C) puts the complete string on the clipboard. Export… (⌘E) writes it to a .txt file. Both always use the whole result, even when a long one is displayed in pages.

If you find yourself doing this often, turn on copy after encoding in B64 ▸ Settings… ▸ General. Dropping the file then is the whole interaction — the result is on your clipboard before you have reached for a shortcut.

A whole camera roll

Drop the folder into Batch (⌘3) and every HEIC in it is encoded in one pass, with anything unsupported listed rather than dropped. How to convert a folder of images to Base64.

Troubleshooting

The payload decodes here but shows nothing in a browser

That is the HEIC support question rather than an encoding problem. Export the photo as JPEG or PNG and encode that version for anywhere with a mixed audience.

The file was refused

Some files with a .heic extension are not HEIC inside. The bytes decide; open the file and check what it actually is.

The result is larger than I expected for a small photo

HEIC files often carry more than the single image you see — thumbnails, depth maps, auxiliary data. All of it is in the file, so all of it is encoded. The Inspector shows the source size, which is where the surprise usually is.