You publish photos on websites, in e-books or through clients, and every time someone has to write alt text from scratch, or skips it. You want the description to live in the file, in the field made for it, so every system that uses the photo can pick it up.
Do it in Parergon
- 01
Write the alt text
In the Info panel’s Editor tab, fill in Alt Text (Accessibility) in the Descriptive section: a sentence or two on what the image shows and why it is there, written to be read aloud. Saving one photo counts as one of the free tier’s five daily edits.
- 02
Add an extended description when needed
For charts, maps and detailed images, keep the alt text as a short summary and put the detail in Extended Description (Accessibility). Do not repeat the alt text there.
- 03
Add other languages
Open the Languages section of the field to store the alt text in other languages beside the default (Pro). On Macs with Apple Intelligence, Apple’s Writing Tools work in both fields, to shorten or proofread what you wrote.
Both fields are stored in XMP, as Iptc4xmpCore:AltTextAccessibility and ExtDescrAccessibility. The legacy IPTC IIM record has no equivalent, so an app that reads only IIM will not see them. Parergon’s counter allows up to 2,000 characters; IPTC recommends a couple of sentences.
Why this happens
Alt text is usually typed into a website’s media library, per site and per page, so the same photo is described again everywhere, or not at all. In 2021 IPTC added two fields, Alt Text (Accessibility) and Extended Description (Accessibility), so the description can be embedded once and travel with the file.
Alt text is not the caption. A caption is shown beside the photo and often names who, where and when. Alt text stands in for the image for someone who cannot see it, so it says what the picture shows and why it matters. IPTC advises against copying the caption or the surrounding text into it.
Other ways to do it on a Mac
- Adobe Bridge and Photo Mechanic
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Both support the two IPTC accessibility fields, so you can fill them in alongside the rest of your IPTC metadata.
- ExifTool (free, Terminal)
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The first command writes the alt text; the second adds a Dutch version beside it, using a language code after the tag name.
exiftool "-XMP-iptcCore:AltTextAccessibility=A lapwing standing in a wet meadow" photo.jpg exiftool "-XMP-iptcCore:AltTextAccessibility-nl=Een kievit in een natte weide" photo.jpg
Questions
What is the difference between alt text and a caption?
A caption is read by everyone, next to the photo, and adds context such as names, places and dates. Alt text replaces the photo for people using a screen reader, so it describes what is in the picture and why it is there. A photo can need both, and they should not be identical.
How long should alt text be?
Short: IPTC recommends a sentence or two, and some editors flag alt text longer than about 250 characters. Put anything longer in Extended Description (Accessibility).
Will my website use the embedded alt text?
Only if your publishing system reads it. Some do, and many still ignore embedded metadata, so check yours. Even then, the field keeps the description with the photo for the next system, client or archive.
Can Parergon write alt text for me?
Not as a draft. Draft Description writes a caption, which serves a different purpose. Writing Tools can shorten or proofread alt text you wrote, on Macs with Apple Intelligence.
Go deeper: Alt Text (Accessibility) in the field reference.