428 vs 412: Precondition Required vs Precondition Failed
428 and 412 can look similar in logs, but they tell clients, crawlers, and API consumers different things.
| Aspect | 428 | 412 |
|---|---|---|
| Meaning | Precondition Required describes how the server processed the request and what the client should do next. | Precondition Failed describes how the server processed the request and what the client should do next. |
| Typical use case | HTTP 428 Precondition Required indicates a client errors response outcome. | HTTP 412 Precondition Failed indicates a client errors response outcome. |
| Caching/client behavior | Check cache headers and downstream behavior for 428. | Check cache headers and downstream behavior for 412. |
| SEO implications | Search crawlers interpret 428 according to client-errors semantics. | Search crawlers interpret 412 according to client-errors semantics. |
| API/backend impact | API clients may branch logic specifically on 428. | API clients may branch logic specifically on 412. |
When to use one vs the other
Use 428 when the response should communicate precondition required behavior; use 412 when precondition failed is the accurate protocol signal.
A frequent mistake is swapping 428 and 412 for convenience; that causes client retry bugs, incorrect cache signals, and misleading monitoring data.
Decision summary: if user agents should receive the Precondition Required signal, return 428; if they should receive Precondition Failed, return 412.
FAQ
What is the biggest difference between 428 and 412?
428 communicates Precondition Required, while 412 communicates Precondition Failed. Choosing the right one keeps clients and intermediaries predictable.
Do 428 and 412 have SEO or caching impact?
Yes. Search engines and caches interpret status classes differently. Use each code according to its semantics to avoid accidental indexing, stale responses, or crawl inefficiency.
Can APIs safely return 428 instead of 412?
Only when it matches contract semantics. API clients often branch logic by exact code, so swapping them can break retries, auth handling, or user-facing errors.
Related guides: 428 Precondition Required · 412 Precondition Failed