Conditional Requests & Concurrency
Headers that make a request conditional on the state of a resource — the difference between a safe update and a lost one.
13 headers, ordered by how many providers in the catalog declare them.
ETag
147 providers
regulated
4 spellings
Defined for caching, used by APIs for concurrency control, and mandated by name inside a US health IT certification programme.
If-Match
106 providers
regulated
3 spellings
The If-Match HTTP header — conditional requests & concurrency, RFC 9110, declared by 106 providers in the API Evangelist catalog.
If-None-Match
102 providers
3 spellings
The If-None-Match HTTP header — conditional requests & concurrency, RFC 9110, declared by 102 providers in the API Evangelist catalog.
If-Modified-Since
60 providers
3 spellings
The If-Modified-Since HTTP header — conditional requests & concurrency, RFC 9110, declared by 60 providers in the API Evangelist catalog.
Last-Modified
43 providers
2 spellings
The Last-Modified HTTP header — conditional requests & concurrency, RFC 9110, declared by 43 providers in the API Evangelist catalog.
If-Unmodified-Since
12 providers
2 spellings
The If-Unmodified-Since HTTP header — conditional requests & concurrency, RFC 9110, declared by 12 providers in the API Evangelist catalog.
Isolation
The Isolation HTTP header — conditional requests & concurrency, not observed in the catalog.
If-Schedule-Tag-Match
The If-Schedule-Tag-Match HTTP header — conditional requests & concurrency, RFC 6338, not observed in the catalog.
If-Range
The If-Range HTTP header — conditional requests & concurrency, RFC 9110, not observed in the catalog.
OData-Isolation
The OData-Isolation HTTP header — conditional requests & concurrency, not observed in the catalog.
Schedule-Tag
The Schedule-Tag HTTP header — conditional requests & concurrency, RFC 6338, not observed in the catalog.
Set-Txn
The Set-Txn HTTP header — conditional requests & concurrency, RFC 9967, not observed in the catalog.
If
The If HTTP header — conditional requests & concurrency, RFC 4918, not observed in the catalog.