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The direct difference
HTTP methods describe intent. RFC 9110 defines PUT as a request for the target resource’s state to be created or replaced with the state in the request representation. The client identifies that target URI. POST requests that the target resource process the enclosed representation according to its own, resource-specific semantics.
In practical terms:
- Choose
PUTwhen the client knows the URI whose state it wants to establish. - Choose
POSTwhen the target should decide how to process the submission, such as creating a resource, appending data, posting a message or handling form fields.
Neither method is universally available on every endpoint. The server decides which methods a resource supports and what its application-level rules are.
PUT explained
What a PUT request means
A PUT request says, in effect, “make the resource at this known URI have the state represented by this payload.” For example, a client might send a complete user profile to /users/42. If the server accepts the representation, a later GET of that URI is generally expected to expose an equivalent state, subject to concurrent updates and server-side processing.
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curl -X PUT https://api.example.com/users/42
-H "Content-Type: application/json"
-d '{"name":"Ada Lovelace","email":"[email protected]"}'The URI is selected by the client. That does not require the resource to have existed beforehand. A successful PUT can create a representation at the target URI. RFC 9110 requires 201 Created when the request successfully creates that representation; replacing an existing representation is a different outcome and need not return 201.
PUT is commonly a full replacement
Many APIs use PUT for a complete representation. If a field is omitted, the API may interpret it as absent or reset, although the exact rule is application-specific. Do not assume that every PUT endpoint performs a partial update. Some APIs use PATCH for partial modifications, but PATCH behavior is outside the PUT-versus-POST distinction and must be documented by the service.
POST explained
POST delegates processing to the target
POST is deliberately broad. RFC 9110 describes it as asking the target resource to process the enclosed representation according to that resource’s specific semantics. Examples include submitting form data to a handler, posting a message, appending data to an existing representation and requesting creation of a resource whose final URI the origin server chooses.
curl -X POST https://api.example.com/users
-H "Content-Type: application/json"
-d '{"name":"Ada Lovelace","email":"[email protected]"}'Here the client sends the request to a collection or processing resource and does not need to know the new user’s URI. The server may assign an identifier and return a response describing the result. A POST endpoint can also trigger an action, such as sending an email or starting an import; it is not limited to resource creation.
PUT vs. POST at a glance
| Decision axis | PUT | POST |
|---|---|---|
| Intent | Create or replace the target resource’s state with the enclosed representation. | Have the target process the enclosed representation according to its own semantics. |
| Target URI | The client knows the intended resource URI. | Often a collection or processing URI; the server may select a new resource URI. |
| Idempotency | Idempotent by HTTP semantics. | Not guaranteed idempotent. |
| Can create? | Yes, at the known target URI; successful creation requires 201 Created. | Yes, among several possible uses. |
| Typical retry posture | Identical requests generally may be retried after an uncertain network result. | Do not automatically retry unless the operation is known to be repeat-safe or you can establish that the first request was not applied. |
| Who defines detailed behavior? | The resource and API contract. | The resource and API contract. |
Idempotency and safe retries
What idempotent means
Idempotency concerns intended server effect: sending an identical request multiple times has the same intended effect as sending it once. It does not mean that every observable detail is identical. A server may record logs, audit entries or revision history for each request even when the resource ends in the same state.
Why PUT is easier to retry
Suppose a client sends a PUT and the connection fails before the response arrives. The server might have applied the request, or the failure might have occurred first. Repeating the identical PUT still asks for the same target state, so HTTP’s idempotency property makes an automatic retry generally appropriate.
curl --retry 3 --retry-all-errors -X PUT
https://api.example.com/users/42
-H "Content-Type: application/json"
-d '{"name":"Ada Lovelace","email":"[email protected]"}'Retry policies still need limits, timeouts and authentication handling. Idempotency does not protect you from a payload that contains a server-side action with additional effects; the endpoint contract remains authoritative.
Why POST needs more care
POST is not guaranteed idempotent. Repeating a request that creates an order, charges a card or sends a message could perform the operation twice. A client should not automatically repeat a non-idempotent request unless it knows the operation is safe to repeat or can determine that the original was not applied.
Some services make a particular POST repeat-safe with an idempotency key or another application rule. That is an API feature, not a property you can assume from the method name. Follow the service’s documentation and preserve the same key when retrying an operation designed around one.
How to choose the method
- Identify the intended meaning. If you are setting the representation of one known resource, start with PUT. If you are submitting data for the target to process, start with POST.
- Ask who chooses the URI. A client-known URI fits PUT. If the server allocates the URI, POST is the standards-aligned choice.
- Decide whether repetition must be safe. PUT’s semantics support retries after uncertain outcomes. Treat POST as non-repeatable unless the endpoint explicitly supplies a safe retry mechanism.
- Read the endpoint contract. Confirm required fields, whether the representation is complete, accepted methods, authentication, concurrency controls and response handling.
- Test failure paths. Simulate timeouts and lost responses, then verify whether the server state and client retry behavior match the contract.
Common mistakes
“PUT always means update”
False. PUT can create a resource when no representation exists at the target URI. A successful creation returns 201 Created. The method expresses replacement or establishment of state, not merely editing an existing record.
“POST always means create”
False. POST can process forms, append data, publish messages or invoke other resource-specific processing. Creation is one possible use.
“PUT has no side effects”
Idempotency describes the intended effect on the target resource. Logging, metrics, notifications or revision records can still change with every request.
“Every API follows REST examples exactly”
Standards define method semantics, but implementations choose which methods to expose and how to model resources. A real endpoint may reject PUT, use POST for an action, or document a repeat-safe POST. Use the API’s contract rather than a URL naming convention alone.
Troubleshooting method errors
405 Method Not Allowed
The resource does not support the method at that URI, or the route is different from the one you intended. Check the endpoint documentation, URL, authentication context and any advertised Allow response header. Do not switch methods blindly: determine which resource you are addressing.
400 or 422 validation failure
The method may be correct but the representation is not. Verify JSON syntax, content type, required fields and whether PUT expects a complete representation rather than a partial object.
Rank #4
201 versus another successful status
For PUT, 201 specifically indicates that the request created the target representation. A replacement outcome is not the same event. For POST, status-code details depend on the endpoint’s processing contract; do not infer the result from the method alone.
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This is a warning sign for POST. Stop blind retries, inspect whether the first request was applied, and use the service’s documented idempotency-key or deduplication mechanism when available. For PUT, check that retries are byte-for-byte or semantically identical and that no client-generated changing fields defeat the intended effect.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Performance, reliability and concurrency
PUT’s retry property can simplify recovery from transient network failures, but it does not solve concurrent writes. Two clients can replace the same resource in sequence. If lost updates matter, use the API’s documented versioning, precondition or conflict mechanism.
POST may be the right choice for work that is naturally an event or command rather than a durable representation. Because the target controls processing, clients should expect endpoint-specific validation, asynchronous handling and response formats. Measure and tune timeouts according to the service contract; never infer reliability from the method name.
Testing an API workflow
Use a small, repeatable sequence: send the request, record the status and response headers, GET the resource when applicable, then repeat the original request to observe whether the documented effect is stable. Test a dropped connection or client timeout separately from a clear HTTP error, because retry decisions differ.
Best Value
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cURL (see the ScreenshotNeo documentation):
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpPython:
import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
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Frequently Asked Questions
Is PUT safer than POST?
Neither method is inherently safer. Security depends on authentication, authorization, validation, transport protection and the endpoint implementation. PUT’s distinct advantage is idempotent intended effect, not stronger access control.
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Can a PUT request use a different URI from the resource it changes?
The target URI is the resource whose state PUT asks the server to create or replace. If an API uses a separate command or processing URI, its contract may call for POST instead.
Should I use PUT for partial updates?
Only if that endpoint explicitly defines PUT as partial. Many APIs treat PUT as a complete representation and reserve PATCH for partial changes, but the service documentation decides.
The Bottom Line
Use PUT when the client knows the target URI and wants that resource’s state established or replaced. Use POST when the target should process submitted data under its own rules. Remember the operational difference: PUT is idempotent by HTTP semantics; POST is not guaranteed to be.
Quick Recap
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