When should I use GET or POST method? What's the difference between them?

Question

What's the difference when using GET or POST method? Which one is more secure? What are (dis)advantages of each of them?

(similar question)

Terhune

Get doesn't have a body so in practice means you are limited to name -> value pairs as data structure due the lack of any query string encoding format for more complex structure. If you need to handle more complex data structures in your requests (i.e. an array, object etc) you need to use POST and perhaps more advanced formats(json/xml). Shortly said: don't use GET unless you really have to(i.e. the URL/resource must be discoverable). – Benoite

Possible duplicate of When do you use POST and when do you use GET? – Reconstructionism

Answer 1

It's not a matter of security. The HTTP protocol defines GET-type requests as being idempotent, while POSTs may have side effects. In plain English, that means that GET is used for viewing something, without changing it, while POST is used for changing something. For example, a search page should use GET, while a form that changes your password should use POST.

Also, note that PHP confuses the concepts a bit. A POST request gets input from the query string and through the request body. A GET request just gets input from the query string. So a POST request is a superset of a GET request; you can use $_GET in a POST request, and it may even make sense to have parameters with the same name in $_POST and $_GET that mean different things.

For example, let's say you have a form for editing an article. The article-id may be in the query string (and, so, available through $_GET['id']), but let's say that you want to change the article-id. The new id may then be present in the request body ($_POST['id']). OK, perhaps that's not the best example, but I hope it illustrates the difference between the two.

Carey

There is definately a security aspect to the difference between GET and POSTs. A malicious site can stick an arbitrary GET request in an image tag for instance, causing users to do a GET against another server. If this GET is like otherserver/deletemyaccount then bad things happen. – Sidonia

What I meant was that contents of $_POST is not magically hidden from malicious users. There are obviously security aspects to all thing programming. – Carey

This post doesn't answer the question completely because he doesn't mention of the security implications. The top part is good as long as the spelling error "pain English" is changed to "plain English". The bottom part is too hard to follow. On the whole, much better than my post tho. :-) – Massy

@FrankSchwieterman well if you make your GET-requests idempotent, which you should, that won't be a problem ;) – Monteiro

" A POST request gets input from the query string and through the request body." IMHO this is incorrect. To use either input you need to use $_REQUEST. $_POST does not get the url entries. – Mullah

@Frank Schwieterman I know this post is old, but delete my account is not idempotent and should not be using get. – Charisecharisma

Is POST a superset of GET? Or is there anything than can be done with GET that cannot be done with POST? – Stranger

@Stranger - from a technical perspective, you could say that POST is a superset of GET, in that it has a body component, which a GET doesn't. I don't think it makes too much sense to think of it that way though, since the two have very different semantics. A GET request is idempotent - e.g. it is cacheable and it's safe to re-issue. A POST has no such guarantees and is generally unsafe to re-issue. – Carey

@troelskn: Good point about GET is idempotent, and thus eligible for caching. So it is a good idea not to think of POST as a superset of GET! – Stranger

Can you do a post request, without starting out by making a get request (from client side). Or are you somehow forced to make a get request first? – Pascual

@Pascual Yes, you can certainly make a POST without first making a GET. It's a core principle of HTTP that there is no continuity between requests. – Carey

@FrankSchwieterman — A malicious site could create a form element with method=post and submit it with JavaScript. Making the correct choice between POST and GET does not save you from CSRF attacks. (It does save you from precachers and spiders though). – Grime

If the endpoint accepts a file and return a line from the file (no data creation or changing or database is involved), then should the endpoint be GET or POST? – Rosannarosanne

Answer 2

When the user enters information in a form and clicks Submit , there are two ways the information can be sent from the browser to the server: in the URL, or within the body of the HTTP request.

The GET method, which was used in the example earlier, appends name/value pairs to the URL. Unfortunately, the length of a URL is limited, so this method only works if there are only a few parameters. The URL could be truncated if the form uses a large number of parameters, or if the parameters contain large amounts of data. Also, parameters passed on the URL are visible in the address field of the browser not the best place for a password to be displayed.

The alternative to the GET method is the POST method. This method packages the name/value pairs inside the body of the HTTP request, which makes for a cleaner URL and imposes no size limitations on the forms output. It is also more secure.

Abri

because its harder to change? you can change GET in the address bar, but its not that easy with POST. – Abri

The server can't trust the client. Designing your application around false assumptions, is far from secure. – Carey

openid is also not save, because it can be broken? – Abri

I believe this is the most clear explanation -- difference about the placement of the data sent. Thank you. – Penland

The client can also make a get request with curl or ajax and write whatever he wants. – Nitz

Answer 3

The best answer was the first one.

You are using:

• GET when you want to retrieve data (GET DATA).
• POST when you want to send data (POST DATA).

Beefeater

What is request/response service pattern is used and you want to do both? ;) I would prefer to use POST in most of the cases when I need to have a response back. – Seineetmarne

Generally that is true. GET is perfectly capable of 'sending' data too, so not a very accurate answer. – Curate

Answer 4

There are two common "security" implications to using GET. Since data appears in the URL string its possible someone looking over your shoulder at Address Bar/URL may be able to view something they should not be privy to such as a session cookie that could potentially be used to hijack your session. Keep in mind everyone has camera phones.

The other security implication of GET has to do with GET variables being logged to most web servers access log as part of the requesting URL. Depending on the situation, regulatory climate and general sensitivity of the data this can potentially raise concerns.

Some clients/firewalls/IDS systems may frown upon GET requests containing an excessive amount of data and may therefore provide unreliable results.

POST supports advanced functionality such as support for multi-part binary input used for file uploads to web servers.

POST requires a content-length header which may increase the complexity of an application specific client implementation as the size of data submitted must be known in advance preventing a client request from being formed in an exclusively single-pass incremental mode. Perhaps a minor issue for those choosing to abuse HTTP by using it as an RPC (Remote Procedure Call) transport.

Others have already done a good job in covering the semantic differences and the "when" part of this question.

Vietnamese

Answer 5

I use GET when I'm retrieving information from a URL and POST when I'm sending information to a URL.

Mouthpart

but you can use GET to send as well. The difference is the format (in the url (GET) or in the request (POST)). – Cynar

If the endpoint accepts a file and return a line from the file (no data creation or changing or database is involved), then should the endpoint be GET or POST? – Rosannarosanne

Answer 6

You should use POST if there is a lot of data, or sort-of sensitive information (really sensitive stuff needs a secure connection as well).

Use GET if you want people to be able to bookmark your page, because all the data is included with the bookmark.

Just be careful of people hitting REFRESH with the GET method, because the data will be sent again every time without warning the user (POST sometimes warns the user about resending data).

Purveyor

If the endpoint accepts a file and return a line from the file (no data creation or changing or database is involved), then should the endpoint be GET or POST? – Rosannarosanne

@Rosannarosanne POST. In this case, mostly because POST is built to handle file uploads and standard GET isn't. You'd have to send the file every time the page loads, so it makes sense to just use standard POST instead of GET+file which would break GET's expectation that a URL should give more-or-less the same results every time. – Purveyor

Answer 7

This W3C document explains the use of HTTP GET and POST.

I think it is an authoritative source.

The summary is (section 1.3 of the document):

• Use GET if the interaction is more like a question (i.e., it is a safe operation such as a query, read operation, or lookup).
• Use POST if:
  • The interaction is more like an order, or
  • The interaction changes the state of the resource in a way that the user would perceive (e.g., a subscription to a service), or
  • The user be held accountable for the results of the interaction.

Phio

I think that can be further summarized as this: GET when the state of the server isn't changed, POST when it is. – Sizing

Answer 8

Get and Post methods have nothing to do with the server technology you are using, it works the same in php, asp.net or ruby. GET and POST are part of HTTP protocol. As mark noted, POST is more secure. POST forms are also not cached by the browser. POST is also used to transfer large quantities of data.

Grouchy

Answer 9

The reason for using POST when making changes to data:

• A web accelerator like Google Web Accelerator will click all (GET) links on a page and cache them. This is very bad if the links make changes to things.
• A browser caches GET requests so even if the user clicks the link it may not send a request to the server to execute the change.
• To protect your site/application against CSRF you must use POST. To completely secure your app you must then also generate a unique identifier on the server and send that along in the request.

Also, don't put sensitive information in the query string (only option with GET) because it shows up in the address bar, bookmarks and server logs.

Hopefully this explains why people say POST is 'secure'. If you are transmitting sensitive data you must use SSL.

Befit

Answer 10

GET and POST are HTTP methods which can achieve similar goals

GET is basically for just getting (retrieving) data, A GET should not have a body, so aside from cookies, the only place to pass info is in the URL and URLs are limited in length , GET is less secure compared to POST because data sent is part of the URL

Never use GET when sending passwords, credit card or other sensitive information!, Data is visible to everyone in the URL, Can be cached data . GET is harmless when we are reloading or calling back button, it will be book marked, parameters remain in browser history, only ASCII characters allowed.

POST may involve anything, like storing or updating data, or ordering a product, or sending e-mail. POST method has a body.

POST method is secured for passing sensitive and confidential information to server it will not visible in query parameters in URL and parameters are not saved in browser history. There are no restrictions on data length. When we are reloading the browser should alert the user that the data are about to be re-submitted. POST method cannot be bookmarked

Fastigium

" A GET should not have a body" - what do you mean by that? – Pained

Answer 11

All or perhaps most of the answers in this question and in other questions on SO relating to GET and POST are misguided. They are technically correct and they explain the standards correctly, but in practice it's completely different. Let me explain:

GET is considered to be idempotent, but it doesn't have to be. You can pass parameters in a GET to a server script that makes permanent changes to data. Conversely, POST is considered not idempotent, but you can POST to a script that makes no changes to the server. So this is a false dichotomy and irrelevant in practice.

Further, it is a mistake to say that GET cannot harm anything if reloaded - of course it can if the script it calls and the parameters it passes are making a permanent change (like deleting data for example). And so can POST!

Now, we know that POST is (by far) more secure because it doesn't expose the parameters being passed, and it is not cached. Plus you can pass more data with POST and it also gives you a clean, non-confusing URL. And it does everything that GET can do. So it is simply better. At least in production.

So in practice, when should you use GET vs. POST? I use GET during development so I can see and tweak the parameters I am passing. I use it to quickly try different values (to test conditions for example) or even different parameters. I can do that without having to build a form and having to modify it if I need a different set of parameters. I simply edit the URL in my browser as needed.

Once development is done, or at least stable, I switch everything to POST.

If you can think of any technical reason that this is incorrect, I would be very happy to learn.

Luz

Answer 12

1. GET method is use to send the less sensitive data whereas POST method is use to send the sensitive data.
2. Using the POST method you can send large amount of data compared to GET method.
3. Data sent by GET method is visible in browser header bar whereas data send by POST method is invisible.

Ecclesiastic

Answer 13

Use GET method if you want to retrieve the resources from URL. You could always see the last page if you hit the back button of your browser, and it could be bookmarked, so it is not as secure as POST method.

Use POST method if you want to 'submit' something to the URL. For example you want to create a google account and you may need to fill in all the detailed information, then you hit 'submit' button (POST method is called here), once you submit successfully, and try to hit back button of your browser, you will get error or a new blank form, instead of last page with filled form.

Crellen

Answer 14

I find this list pretty helpful

GET

• GET requests can be cached
• GET requests remain in the browser history
• GET requests can be bookmarked
• GET requests should (almost) never be used when dealing with sensitive data
• GET requests have length restrictions
• GET requests should be used only to retrieve data

POST

• POST requests are not cached
• POST requests do not remain in the browser history
• POST requests cannot be bookmarked
• POST requests have no restrictions on data length

Asphodel

Answer 15

The GET method:

• It is used only for sending 256 character date

• When using this method, the information can be seen on the browser

• It is the default method used by forms

• It is not so secured.

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The POST method:

• It is used for sending unlimited data.

• With this method, the information cannot be seen on the browser

• You can explicitly mention the POST method

• It is more secured than the GET method

• It provides more advanced features

Yarborough

"It is used only for sending 256 character date" — not true. "When using this method, the information can be seen on the browser" — post data is also visible in browsers, it just isn't quite so obvious. "It provides more advanced features" — such as? – Grime

This isn't a terribly useful answer. Incorrect information such as 'it is not so secured' and 'provides more advanced features', and other things mentioned by Quentin. – Ovum