On Sunday January 22nd 2023 between 10:00 and 15:00 UTC/GMT the API database servers will be unavailable due to maintenance. You can see this in your local time zone at Event Time Announcer - OpenStreetMap API Maintenance
We are planning to upgrade the software which runs the main OpenStreetMap database. Unfortunately, we cannot do this without some downtime.
API will NOT allow map editing (using iD, JOSM, etc), and
replication updates will be paused (minutely updates and changeset replication).
We expect that the database upgrade will not take the full duration, and we will try as far as possible to keep the API available in read-only mode, but the API may be briefly unavailable.
At times you may be unable to login to services which requires openstreetmap.org authentication (e.g. community, forum, and help)
Other OpenStreetMap provided services should not be affected except for login - all of the following are expected to function normally:
This depends on the time, the endpoint and the authentication method. Could be either no response at all, or some 4xx or 5xx, and for read only use cases even 200.
I think it would be better to check the results of https://api.openstreetmap.org/api/0.6/capabilities - if any of <status database="online" api="online" gpx="online"/> reports an “offline” status, you can be pretty sure you won’t be able to upload anything, or also log in to the site.
Yes - the capabilities page is the right page to be checking, because you can do this before the user starts editing, and don’t have to identify which API calls will work on different modes.