When the submit button is activated, the form is sent to the program specified by the action attribute. The following example shows how the contents of a user-specified file may be submitted with a form. This example is based on an example from [RFC].
In this example, the user is prompted to enter a name and a list of names of files whose contents should be submitted with the form. Please consult [RFC] for more information about file submissions. This attribute specifies a prompt string for the input field. The user agent may use the value of the prompt attribute as a title for the prompt.
In practice, the input string is restricted to Latin-1 as there is no mechanism for the URL to specify a different character set. When this attribute is not set, the button's behavior is undefined. Possible values: button: Creates a simple push button intended to trigger a script.
This is the default value. They both cause a form to be submitted, but their presentation is different. The buttons contain images by way of the IMG element. When such a button is activated, a client-side script is executed. This name will be paired with any selected values when the form is submitted. The number of rows may be smaller than the number of possible choices. In this case, the user agent should provide a scrolling mechanism for accessing all possible choices.
Traditionally, visual user agents render multiple-selection elements as list boxes, while single-selection elements are rendered as drop-down menus. OPTION Attribute definitions selected When set, this boolean attribute specifies that this option is selected initially or by the user.
In this example, we create a menu that allows the user to select which of seven software components to install.
The first and second components are initially selected but may be deselected by the user. The remaining components are not initially selected. The size attribute states that the menu should only have 4 rows even though the user may select from among 7 options.
The other options must be made available through a scrolling mechanism. The submitted value of each OPTION will be its contents, except where overridden by the value attribute here, in the first two components. This name will be paired with the content of the element when submitted to the server. Users should be able to enter more lines than this, so user agents should provide some means to scroll through the contents of the textarea field when the contents extend beyond the visible area.
Users should be able to enter longer lines than this, so user agents should provide some means to scroll through the contents of the textarea field when the contents extend beyond the visible area. User agents may wrap visible text lines to keep long lines visible without the need for scrolling.
The content of this element provides the initial text presented by the control. Second line of initial text. The character set for submitted data should be ISO Latin-1, unless the server has previously indicated that it can support alternative character sets. The value of this attribute must be the value of the id attribute of some other control in the same document. In the absence of this attribute, the label being defined is associated with its contents.
Labels may be rendered by user agents in a number of ways e. See the section below on access keys for examples. More than one LABEL may be associated with the same control by creating multiple references via the for attribute. The label itself may be positioned before or after the associated control. It's also possible for someone to bypass your HTML entirely and submit the data directly to your server.
If your server-side code fails to validate the data it receives, disaster could strike when improperly-formatted data or data which is too large, is of the wrong type, and so forth is entered into your database.
Browsers that support the url input type automatically provide validation to ensure that only text that matches the standard format for URLs is entered into the input box. The syntax of a URL is fairly intricate.
As mentioned earlier, to make a URL entry required before the form can be submitted you can't leave the field blank , you just need to include the required attribute on the input.
If you need the entered URL to be restricted further than just "any string that looks like a URL," you can use the pattern attribute to specify a regular expression the value must match for the value to be valid. For example, let's say you're building a support page for employees of Myco, Inc. In our simplified form, the user needs to enter the URL of the page that has a problem, and a message describing what is wrong. Since inputs of type url validate against both the standard URL validation and the specified pattern , you can implement this easily.
Let's see how:. First of all, the required attribute is specified, making it mandatory that a valid email address be provided. Second, in the url input we set pattern to ". This simple regular expression requests a string that has any number of characters, followed by a dot, followed by "myco", followed by a dot, followed by any number of characters. And because the browser runs both the standard URL filter and our custom pattern against the specified text, we wind up with a validation which says "make sure this is a valid URL, and also in a Myco domain.
It's advisable to use the title attribute along with pattern. If you do, the title must describe the pattern; it should explain what format the data should take on, rather than any other information. That's because the title may be displayed or spoken as part of a validation error message. For example, the browser might present the message "The entered text doesn't match the required pattern.
If your title is something like "URL", the result would be the message "The entered text doesn't match the required pattern. URL", which is not a good user experience. That's why, instead, we specify the string "The URL must be in a myco domain". By doing that, the resulting full error message might be something like "The entered text doesn't match the required pattern. The URL should be in a myco domain.
Note: If you run into trouble while writing your validation regular expressions and they're not working properly, check your browser's console; there may be helpful error messages there to aid you in solving the problem.
There's not much else to say about url type inputs; check the Pattern validation and Using URL inputs sections for numerous examples. You can also find our pattern validation example on GitHub see it running live also. More specifically, there are two possible value formats that will pass validation: An empty string "" indicating that the user did not enter a value or that the value was removed. A single properly-formed absolute URL. This doesn't necessarily mean the URL address exists, but it is at least formatted correctly.
The permitted values for spellcheck are: false Disable spell checking for this element. This header is very important because it tells the server what kind of data is being sent. In human terms, this means: "This is form data that has been encoded into URL parameters. Note: Servers can be configured with a size limit for files and HTTP requests in order to prevent abuse.
Each time you send data to a server, you need to consider security. HTML forms are by far the most common server attack vectors places where attacks can occur. The problems never come from the HTML forms themselves — they come from how the server handles data. The Website security article of our server-side learning topic discusses a number of common attacks and potential defenses against them in detail.
You should go and check that article out, to get an idea of what's possible. So, how do you fight these threats? This is a topic far beyond this guide, but there are a few rules to keep in mind. The most important rule is: never ever trust your users, including yourself; even a trusted user could have been hijacked. Don't assume that you've seen all the possible problems. As we'd alluded to above, sending form data is easy, but securing an application can be tricky. Just remember that a front-end developer is not the one who should define the security model of the data.
It's possible to perform client-side form validation , but the server can't trust this validation because it has no way to truly know what has really happened on the client-side. If you've worked your way through these tutorials in order, you now know how to markup and style a form, do client-side validation, and have some idea about submitting a form.
Skip to main content Skip to search Skip to select language Learn web development Web forms — Working with user data Sending form data Change language. Previous Overview: Forms Once the form data has been validated on the client-side, it is okay to submit the form. Objective: To understand what happens when form data is submitted, including getting a basic idea of how data is processed on the server.
First we'll discuss what happens to the data when a form is submitted. After submitting the form: Open the developer tools. Select "Network" Select "All" Select "foo. This can be very important for two reasons: If you need to send a password or any other sensitive piece of data , never use the GET method or you risk displaying it in the URL bar, which would be very insecure.
In addition, many servers limit the length of URLs they accept. It's more common to use one of the many high quality frameworks that make handling forms easier, such as: Django for Python a bit more heavyweight than Flask , but with more tools and options.
Express for Node. Users interact with forms through named controls. A control's "control name" is given by its name attribute. Each control has both an initial value and a current value, both of which are character strings. Please consult the definition of each control for information about initial values and possible constraints on values imposed by the control. In general, a control's "initial value" may be specified with the control element's value attribute.
The control's "current value" is first set to the initial value. Thereafter, the control's current value may be modified through user interaction and scripts. A control's initial value does not change. Thus, when a form is reset, each control's current value is reset to its initial value. If a control does not have an initial value, the effect of a form reset on that control is undefined.
When a form is submitted for processing, some controls have their name paired with their current value and these pairs are submitted with the form. Authors should specify the scripting language of a push button script through a default script declaration with the META element. Please consult the definitions of these elements for details about specifying different button types.
Several checkboxes in a form may share the same control name. Thus, for example, checkboxes allow users to select several values for the same property. Since user agent behavior differs, authors should ensure that in each set of radio buttons that one is initially "on". The elements used to create controls generally appear inside a FORM element, but may also appear outside of a FORM element declaration when they are used to build user interfaces.
This is discussed in the section on intrinsic events. Note that controls outside a form cannot be successful controls. User agents may interpret this value as the character encoding that was used to transmit the document containing this FORM element. The FORM element acts as a container for controls. It specifies:. A form can contain text and markup paragraphs, lists, etc. The following example shows a form that is to be processed by the "adduser" program when submitted.
The form will be sent to the program using the HTTP "post" method. Please consult the section on form submission for information about how user agents must prepare form data for servers and how user agents should handle expected responses. Further discussion on the behavior of servers that receive form data is beyond the scope of this specification. Application designers should note that this mechanism affords only light security protection.
Although the password is masked by user agents from casual observers, it is transmitted to the server in clear text, and may be read by anyone with low-level access to the network. When a pointing device is used to click on the image, the form is submitted and the click coordinates passed to the server. The x value is measured in pixels from the left of the image, and the y value in pixels from the top of the image. The submitted data includes name. If the server takes different actions depending on the location clicked, users of non-graphical browsers will be disadvantaged.
For this reason, authors should consider alternate approaches:. The following sample HTML fragment defines a simple form that allows the user to enter a first name, last name, email address, and gender. When the submit button is activated, the form will be sent to the program specified by the action attribute. In this next example, the JavaScript function name verify is triggered when the "onclick" event occurs:.
Please consult the section on intrinsic events for more information about scripting and events. The following example shows how the contents of a user-specified file may be submitted with a form. The user is prompted for his or her name and a list of file names whose contents should be submitted with the form. The buttons contain images by way of the IMG element.
Recall that authors must provide alternate text for an IMG element. This is particularly helpful when the user must choose from a long list of options; groups of related choices are easier to grasp and remember than a single long list of options. Zero or more choices may be pre-selected for the user.
User agents should determine which choices are pre-selected as follows:. Implementors are advised that future versions of HTML may extend the grouping mechanism to allow for nested groups i. This will allow authors to represent a richer hierarchy of choices. When rendering a menu choice , user agents should use the value of the label attribute of the OPTION element as the choice.
In this example, we create a menu that allows the user to select which of seven software components to install.
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