HTML <isindex> Tag
The <isindex> defines search string in the current document. The tag isn’t supported by browsers. Learn what to use instead.
The <isindex> tag was an early, primitive way to add a search box to a web page. It rendered a single-line text input; when the user typed a keyword and pressed Enter, the browser submitted that value to the server as a query string (for example, ?keyword). It predates the modern <form> element.
The <isindex> tag is obsolete and has been removed from HTML. It is a deprecated HTML tag that modern browsers no longer render. Do not use it. To build a search box today, use a <form> containing an <input> field, as shown below.
What <isindex> Did
When a browser encountered <isindex>, it inserted a single-line text field, usually preceded by a short prompt label (default text such as "This is a searchable index. Enter search keywords:"). Typing a value and pressing Enter sent that value back to the document's own URL as a URL-encoded query string. The server then returned a result based on the keyword.
In other words, <isindex> was a built-in, one-field search box from the era before forms existed. Once the flexible <form> and <input> elements were standardized, <isindex> became redundant.
Modern Replacement
Replace <isindex> with a real form. The example below produces the same kind of single-field search box, but it works in every modern browser and you control where the data is sent and how it is submitted:
<form action="/search" method="get">
<label for="search">Search:</label>
<input type="search" id="search" name="q" placeholder="Enter search keywords">
<button type="submit">Go</button>
</form>Submitting this form with the keyword html sends a request to /search?q=html — the same query-string mechanism <isindex> relied on, but explicit and standards-compliant. Use <input type="text"> if you do not want the search-specific styling that some browsers apply to type="search".
Why <isindex> Was Removed
- It was non-semantic and confusing. A lone tag silently created a form control, with no
<form>, no<input>, and no obvious submit target. - It was inflexible. You could not choose the request method, the submit URL, or add more than one field.
- It was superseded.
<form>and<input>do everything<isindex>did, and far more.
For a full list of tags you should no longer use, see Deprecated HTML Tags.
Attributes
<isindex> supported only one attribute of its own:
| Attribute | Value | Description |
|---|---|---|
| prompt | text | Specifies the text label shown in front of the search input field. If omitted, the browser displays its own default prompt. |
The tag had no action attribute — the submitted query was sent to the document's own URL. Use a <form> with an action attribute to control the submit target instead.