从w3schools.com:

What is HTTP? The Hypertext Transfer Protocol (HTTP) is designed to enable communications between clients and servers. HTTP works as a request-response protocol between a client and server. A web browser may be the client, and an application on a computer that hosts a web site may be the server. Example: A client (browser) submits an HTTP request to the server; then the server returns a response to the client. The response contains status information about the request and may also contain the requested content. Two HTTP Request Methods: GET and POST Two commonly used methods for a request-response between a client and server are: GET and POST. GET – Requests data from a specified resource POST – Submits data to be processed to a specified resource

在这里我们区分主要的区别:

短的版本

GET:通常用于已提交的搜索请求，或者任何您希望用户能够再次调出确切页面的请求。

GET的优点:

url可以安全地添加书签。 页面可以安全地重新加载。

GET的缺点:

变量作为名称-值对通过url传递。(安全风险) 可以传递的变量数量有限。(基于浏览器。例如，Internet Explorer被限制为2048个字符。)

POST:用于更高安全性的请求，其中数据可能用于更改数据库，或者您不希望别人添加书签的页面。

POST的优点:

url中不显示名称-值对。(安全+= 1) 可以通过POST传递无限数量的名称-值对。参考。

POST的缺点:

使用POST数据的页面不能被书签。(如果你愿意的话。)

完整版

直接来自超文本传输协议——HTTP/1.1:

9.3 GET The GET method means retrieve whatever information (in the form of an entity) is identified by the Request-URI. If the Request-URI refers to a data-producing process, it is the produced data which shall be returned as the entity in the response and not the source text of the process, unless that text happens to be the output of the process. The semantics of the GET method change to a "conditional GET" if the request message includes an If-Modified-Since, If-Unmodified-Since, If-Match, If-None-Match, or If-Range header field. A conditional GET method requests that the entity be transferred only under the circumstances described by the conditional header field(s). The conditional GET method is intended to reduce unnecessary network usage by allowing cached entities to be refreshed without requiring multiple requests or transferring data already held by the client. The semantics of the GET method change to a "partial GET" if the request message includes a Range header field. A partial GET requests that only part of the entity be transferred, as described in section 14.35. The partial GET method is intended to reduce unnecessary network usage by allowing partially-retrieved entities to be completed without transferring data already held by the client. The response to a GET request is cacheable if and only if it meets the requirements for HTTP caching described in section 13. See section 15.1.3 for security considerations when used for forms. 9.5 POST The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line. POST is designed to allow a uniform method to cover the following functions: Annotation of existing resources; Posting a message to a bulletin board, newsgroup, mailing list, or similar group of articles; Providing a block of data, such as the result of submitting a form, to a data-handling process; Extending a database through an append operation. The actual function performed by the POST method is determined by the server and is usually dependent on the Request-URI. The posted entity is subordinate to that URI in the same way that a file is subordinate to a directory containing it, a news article is subordinate to a newsgroup to which it is posted, or a record is subordinate to a database. The action performed by the POST method might not result in a resource that can be identified by a URI. In this case, either 200 (OK) or 204 (No Content) is the appropriate response status, depending on whether or not the response includes an entity that describes the result.

重要的一点是，你通过GET提交的任何东西都会通过URL被暴露。其次，正如Ceejayoz所说，URL的字符数量是有限制的。

1.3 HTTP GET / POST选择快速检查

在以下情况下使用GET:

    The interaction is more like a question (i.e., it is a safe operation such as a query, read operation, or lookup).

在以下情况下使用POST:

    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.

源。

Gorgapor, mod_rewrite仍然经常使用GET。它只是允许将一个更友好的URL转换为一个带有GET查询字符串的URL。

使用POST进行破坏性操作，例如创建(我知道这很讽刺)、编辑和删除，因为您不能在浏览器的地址栏中点击POST操作。当允许一个人调用一个动作是安全的时候使用GET。URL是这样的:

http://myblog.org/admin/posts/delete/357

应该带你到一个确认页面，而不是简单地删除项目。这样避免事故要容易得多。

POST也比GET更安全，因为您没有将信息粘贴到URL中。因此，使用GET作为收集密码或其他敏感信息的HTML表单的方法并不是最好的主意。

最后一点注意:POST可以比GET传输更多的信息。“POST”没有传输数据的大小限制，而“GET”限制为2048个字符。