You leave 2,400 RAW files tagging overnight. In the morning the job is done: there is an .xmp file sitting next to every .NEF on disk. You open the folder in Capture One, look at the Keywords tool, and it is empty.
Nothing is broken. Capture One simply has not been told to read those files yet, and the setting that controls it is off the beaten path. This is the part of the workflow where tagged shoots quietly stall, so it is worth getting exactly right.
What actually lands on disk
RaceTagger treats RAW files and JPEGs differently, because the file formats force it to.
For RAW files, the metadata goes into a sidecar. RaceTagger creates _DSC4471.xmp next to _DSC4471.NEF — the basename is replaced rather than appended, which is the long-standing Adobe-style convention for RAW sidecars. The RAW file itself is never modified. That covers the eight RAW extensions RaceTagger handles: NEF, ARW, CR2, CR3, ORF, RW2, DNG and generic RAW.
For JPEGs, there is no sidecar. The metadata is written into the file itself, so it travels wherever the JPEG goes — including to a client or an agency FTP, with no second file to remember.
Inside the sidecar, race numbers land in dc:subject, the standard XMP keyword field. That is the same field Capture One populates from its own Keywords tool, which is why the two can meet at all. A description goes into dc:description, and the IPTC fields your agency cares about — headline, creator, credit, location, event — are written in the standard photoshop: and Iptc4xmp namespaces rather than in anything proprietary.
One behavior matters more than the rest, and it cuts both ways. If a sidecar already exists, RaceTagger edits it in place rather than overwriting the file, so ratings and color labels you set in Capture One before tagging survive. The keyword field does not: dc:subject is rewritten as a block, so keywords already in that field are replaced by the tagging run, not merged with it.
That matters if you keyword in Capture One first. Sync your keywords out to the sidecar and then tag, and the ones you typed are gone. Tag first and keyword afterwards, and both sets end up in the catalog. Either way, this is the thing to verify on a copy of one shoot before you trust it with a season.
If the terms above are new, the XMP sidecar primer covers the format itself; this article is about the handoff.
What Capture One does with a sidecar
Capture One reads metadata from four places: embedded EXIF, embedded IPTC-IIM, embedded XMP, and the .xmp sidecar. Only the sidecar can be written back to. What travels through it is metadata — keywords, ratings, color labels — not adjustments. Your exposure and color work lives in the session or catalog database and stays there.
The behavior is governed by one preference. Go to Capture One → Preferences on macOS, or Edit → Preferences on Windows, open the Image tab, and find Auto Sync Sidecar XMP in the Metadata section. There are three options:
- Full Sync — two-way. Capture One writes its metadata changes out to the sidecar, creates one if it does not exist, and loads anything present in the sidecar that it does not already have.
- Load — one-way, inbound. Capture One reads the sidecar into the session or catalog, but never writes back to it.
- None — no automatic sync at all. Manual syncing still works.
If yours is set to None, which it may well be, the sidecars are invisible and will stay that way no matter how many times you restart. That single dropdown is the answer to most "my keywords disappeared" afternoons.
You do not have to rely on the automatic setting. Right-click a selection in the Browser and you get Load Metadata, which pulls from the sidecar into Capture One, and Sync Metadata, which performs the two-way sync. On a folder you have just finished tagging, Load Metadata on a select-all is the fastest way to bring a shoot in.
The order of operations that saves the afternoon
There are two sane sequences, and one that causes trouble.
Tag first, then import. Point RaceTagger at the card dump, let it write the sidecars, then import the folder into Capture One. The keywords come in with the images and there is nothing to reconcile. This is the simpler path and the one to prefer when you are shooting an event you will cull later.
Import first, then tag. If the folder is already in a session because you were culling on site, run RaceTagger over the same files, then select all and Load Metadata. Capture One picks up the numbers without disturbing the ratings you set while culling.
The sequence that costs you time is renaming or moving files between those two steps. The sidecar is bound to its RAW by filename and location. Rename _DSC4471.NEF to MONZA_074.NEF in Capture One after RaceTagger has written _DSC4471.xmp, and the pairing is gone — the sidecar is still on disk, still full of correct keywords, and no longer attached to anything. Rename before tagging, or after the metadata has been loaded into the catalog, but not between.
What does not travel
A few honest limits, so they do not surprise you mid-deadline.
Keywords written by RaceTagger are flat. A race number becomes a keyword; it does not arrive as a hierarchy under a parent like Event > Class > Number. If your library depends on hierarchical keywords, you will be building that structure in Capture One yourself.
Adjustments never move through XMP in either direction. This is a Capture One design decision, not a limitation of the tagging step, and it is the right one — but it means a sidecar is not a backup of your work.
And the numbers themselves are read from the photograph, which means dirt, motion blur and a bib folded into a runner's waistband all cost accuracy. RaceTagger is reliable on clean, front-facing numbers and gets less so as the frame gets worse. The workflow above is built on the assumption that you will still spot-check a set before it goes to a client.
Why the plumbing is worth an afternoon
A race number that exists only in a database you cannot search from your editing application is not much use. The point of writing standard fields into a standard sidecar is that the number becomes a filter in the tool you already work in: type it into the Capture One search field and the frames for that competitor come up, ready to export as a set.
The tagging is the part that scales. The handoff is the part that decides whether any of it reaches the person waiting for the photos.