Write it once, carry it with the file
In 2021 the IPTC added two accessibility properties to its photo metadata standard: a short alt text and an extended description. A picture that carries them brings its description along wherever the file goes, and a system that reads them — WordPress has done so on upload since 7.0 — can fill in the alt attribute without anyone retyping it.
This page writes those two fields into the XMP block of a JPEG, PNG or WebP file. It parses the file’s structure, replaces or inserts only the XMP part, and copies everything else across unchanged. It then reads the new file back with the same parser, shows what it found, and hashes the image data of both files so the claim that nothing else changed is something you can check.
What it will not do
- It does not write HEIC or AVIF; it can make a JPEG copy instead.
- It does not edit EXIF or IPTC-IIM fields, camera data or location.
- It does not make social networks read the field. They do not, today.
Questions people ask
Is my picture uploaded?
No. The file is read into this tab, the metadata is written into a copy of its bytes in the tab, and the copy is handed to your browser to save. There is no server here that accepts a file.
Which fields are written?
The IPTC Photo Metadata Standard's accessibility properties, in XMP: Alt Text (Accessibility) and Extended Description (Accessibility). Optionally the alt text is also written as the general description (dc:description), which most photo software shows. EXIF and IPTC-IIM fields are left as they are.
Does it change the picture?
No. JPEG, PNG and WebP are edited as bytes: the XMP block is added or replaced and every byte of image data is copied unchanged. The page hashes the image data before and after (SHA-256) and shows both, so you can see they match.
What reads embedded alt text?
WordPress 7.0 and later reads the IPTC alt text field when a picture is uploaded to the media library, and photo tools that support the IPTC accessibility properties show it. Social networks and browsers do not read it: paste the alt text into those as well.
Can it write HEIC or AVIF?
No. For HEIC, AVIF, GIF, BMP and TIFF the page offers to make a JPEG copy in the tab (quality 0.92) and writes into that instead.
What if the file already has alt text?
It is shown as “Already in the file” and used as the starting draft, labelled From the file. Writing replaces the XMP block with the new fields.
Where to take this next
- Alt textWrite the alt attribute yourself, with the picture open and the findings live.
- Bulk alt textA folder of pictures, each given the answer it earns, reviewed and approved before export.
- Add caption to photoPrint a checked caption under, over or around a photo: strip, band, meme or polaroid.
- Alt text checkerPaste alt text you already have and read the findings. No picture required.
