The Document Base URL Element - HTML - MDN Web Docs - Mozilla

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  1. References
  2. HTML
  3. Elements
  4. <base>
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  • Attributes
  • Usage notes
  • Examples
  • Technical summary
  • Specifications
  • Browser compatibility
  1. HTML
  2. Beginner's tutorials
    1. Your first website: Creating the content
    2. Structuring content with HTML
      1. Basic HTML syntax
      2. What's in the head? Webpage metadata
      3. Headings and paragraphs in HTML
      4. Emphasis and importance
      5. Lists
      6. Structuring documents
      7. Advanced text features
      8. Creating links
      9. Challenge: Marking up a letter
      10. Challenge: Structuring a page of content
      11. HTML images
      12. HTML video and audio
      13. Challenge: Mozilla splash page
      14. HTML table basics
      15. HTML table accessibility
      16. Challenge: Structuring a planet data table
      17. Forms and buttons in HTML
      18. Debugging HTML
  3. Guides
    1. Content categories
    2. Block-level elements
    3. Inline elements
    4. Quirks Mode and Standards Mode
    5. Date and time formats used in HTML
    6. Constraint validation
    7. Microdata
    8. Microformats
    9. Viewport meta tag
    10. Allowing cross-origin use of images and canvas
  4. References
  5. HTML elements
    1. <a>
    2. <abbr>
    3. <acronym> Deprecated
    4. <address>
    5. <area>
    6. <article>
    7. <aside>
    8. <audio>
    9. <b>
    10. <base>
    11. <bdi>
    12. <bdo>
    13. <big> Deprecated
    14. <blockquote>
    15. <body>
    16. <br>
    17. <button>
    18. <canvas>
    19. <caption>
    20. <center> Deprecated
    21. <cite>
    22. <code>
    23. <col>
    24. <colgroup>
    25. <data>
    26. <datalist>
    27. <dd>
    28. <del>
    29. <details>
    30. <dfn>
    31. <dialog>
    32. <dir> Deprecated
    33. <div>
    34. <dl>
    35. <dt>
    36. <em>
    37. <embed>
    38. <fencedframe> Experimental
    39. <fieldset>
    40. <figcaption>
    41. <figure>
    42. <font> Deprecated
    43. <footer>
    44. <form>
    45. <frame> Deprecated
    46. <frameset> Deprecated
    47. <h1>
    48. <head>
    49. <header>
    50. <hgroup>
    51. <hr>
    52. <html>
    53. <i>
    54. <iframe>
    55. <img>
    56. <input>
    57. <ins>
    58. <kbd>
    59. <label>
    60. <legend>
    61. <li>
    62. <link>
    63. <main>
    64. <map>
    65. <mark>
    66. <marquee> Deprecated
    67. <menu>
    68. <meta>
    69. <meter>
    70. <nav>
    71. <nobr> Deprecated
    72. <noembed> Deprecated
    73. <noframes> Deprecated
    74. <noscript>
    75. <object>
    76. <ol>
    77. <optgroup>
    78. <option>
    79. <output>
    80. <p>
    81. <param> Deprecated
    82. <picture>
    83. <plaintext> Deprecated
    84. <portal> Experimental
    85. <pre>
    86. <progress>
    87. <q>
    88. <rb> Deprecated
    89. <rp>
    90. <rt>
    91. <rtc> Deprecated
    92. <ruby>
    93. <s>
    94. <samp>
    95. <script>
    96. <search>
    97. <section>
    98. <select>
    99. <slot>
    100. <small>
    101. <source>
    102. <span>
    103. <strike> Deprecated
    104. <strong>
    105. <style>
    106. <sub>
    107. <summary>
    108. <sup>
    109. <table>
    110. <tbody>
    111. <td>
    112. <template>
    113. <textarea>
    114. <tfoot>
    115. <th>
    116. <thead>
    117. <time>
    118. <title>
    119. <tr>
    120. <track>
    121. <tt> Deprecated
    122. <u>
    123. <ul>
    124. <var>
    125. <video>
    126. <wbr>
    127. <xmp> Deprecated
  6. Global attributes
    1. accesskey
    2. anchor Experimental Non-standard
    3. autocapitalize
    4. autocorrect Experimental
    5. autofocus
    6. class
    7. contenteditable
    8. data-*
    9. dir
    10. draggable
    11. enterkeyhint
    12. exportparts
    13. hidden
    14. id
    15. inert
    16. inputmode
    17. is
    18. itemid
    19. itemprop
    20. itemref
    21. itemscope
    22. itemtype
    23. lang
    24. nonce
    25. part
    26. popover
    27. slot
    28. spellcheck
    29. style
    30. tabindex
    31. title
    32. translate
    33. virtualkeyboardpolicy Experimental
    34. writingsuggestions
  7. Attributes
    1. accept
    2. autocomplete
    3. capture
    4. crossorigin
    5. dirname
    6. disabled
    7. elementtiming
    8. for
    9. max
    10. maxlength
    11. min
    12. minlength
    13. multiple
    14. pattern
    15. placeholder
    16. readonly
    17. rel
    18. required
    19. size
    20. step
  8. <input> types
    1. <input type="button">
    2. <input type="checkbox">
    3. <input type="color">
    4. <input type="date">
    5. <input type="datetime-local">
    6. <input type="email">
    7. <input type="file">
    8. <input type="hidden">
    9. <input type="image">
    10. <input type="month">
    11. <input type="number">
    12. <input type="password">
    13. <input type="radio">
    14. <input type="range">
    15. <input type="reset">
    16. <input type="search">
    17. <input type="submit">
    18. <input type="tel">
    19. <input type="text">
    20. <input type="time">
    21. <input type="url">
    22. <input type="week">
  • Attributes
  • Usage notes
  • Examples
  • Technical summary
  • Specifications
  • Browser compatibility

The <base> HTML element specifies the base URL to use for all relative URLs in a document. There can be only one <base> element in a document.

A document's used base URL can be accessed by scripts with Node.baseURI. If the document has no <base> elements, then baseURI defaults to location.href.

Attributes

This element's attributes include the global attributes.

Warning: A <base> element must have an href attribute, a target attribute, or both. If at least one of these attributes are specified, the <base> element must come before other elements with attribute values that are URLs, such as a <link>'s href attribute.

href

The base URL to be used throughout the document for relative URLs. Absolute and relative URLs are allowed. data: and javascript: URLs are not allowed.

target

A keyword or author-defined name of the default browsing context to show the results of navigation from <a>, <area>, or <form> elements without explicit target attributes. The following keywords have special meanings:

  • _self (default): Show the result in the current browsing context.
  • _blank: Show the result in a new, unnamed browsing context.
  • _parent: Show the result in the parent browsing context of the current one, if the current page is inside a frame. If there is no parent, acts the same as _self.
  • _top: Show the result in the topmost browsing context (the browsing context that is an ancestor of the current one and has no parent). If there is no parent, acts the same as _self.

Usage notes

Multiple <base> elements

If multiple <base> elements are used, only the first href and first target are obeyed — all others are ignored.

In-page anchors

Links pointing to a fragment in the document — e.g. <a href="#some-id"> — are resolved with the <base>, triggering an HTTP request to the base URL with the fragment attached.

For example, given <base href="https://example.com/"> and this link: <a href="#anchor">To anchor</a>. The link points to https://example.com/#anchor.

target may not contain ASCII newline, tab, or <

If the target attribute contains an ASCII newline, tab, or the < character, the value is reset to _blank. This is to prevent dangling markup injection attacks, a script-less attack in which an unclosed target attribute is injected into the page so that any text that follows is captured until the browser reaches a character that closes the attribute.

Open Graph

Open Graph tags do not acknowledge <base>, and should always have full absolute URLs. For example:

html<meta property="og:image" content="https://example.com/thumbnail.jpg" />

Examples

html<base href="https://www.example.com/" /> <base target="_blank" /> <base target="_top" href="https://example.com/" />

Technical summary

Content categories Metadata content.
Permitted content None; it is a void element.
Tag omission Must have a start tag and must not have an end tag.
Permitted parents A <head> that doesn't contain another <base> element.
Implicit ARIA role No corresponding role
Permitted ARIA roles No role permitted
DOM interface HTMLBaseElement

Specifications

Specification
HTML Standard # the-base-element

Browser compatibility

BCD tables only load in the browser

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