3 Advanced

EWW normally uses url-retrieve to fetch the HTML before rendering it, and url-retrieve-synchronously when the value of eww-retrieve-command is sync. It can sometimes be convenient to use an external program to do this, and eww-retrieve-command should then be a list that specifies a command and the parameters. For instance, to use the Chromium browser, you could say something like this:

(setq eww-retrieve-command
      '("chromium" "--headless" "--dump-dom"))

The command should return the HTML on standard output, and the data should use UTF-8 as the charset.

You can view the source of a website with v (eww-view-source). This will open a new buffer *eww-source* and insert the source. The buffer will be set to html-mode if available.

EWW handles cookies through the (url)url package package. You can list existing cookies with C (url-cookie-list). For details about the Cookie handling See (url)Cookies.

Many HTML pages have images embedded in them, and EWW will download most of these by default. When fetching images, cookies can be sent and received, and these can be used to track users. To control when to send cookies when retrieving these images, the shr-cookie-policy variable can be used. The default value, same-origin, means that EWW will only send cookies when fetching images that originate from the same source as the HTML page. nil means “never send cookies when retrieving these images” and t means “always send cookies when retrieving these images”.

When following links in EWW, URLs that match the eww-use-browse-url regexp will be passed to browse-url instead of EWW handling them itself. The action can be further customized by altering browse-url-handlers.

The header line of the EWW buffer can be changed by customizing eww-header-line-format. The format replaces %t with the title of the website and %u with the URL.

The D command (eww-toggle-paragraph-direction) toggles the paragraphs direction between left-to-right and right-to-left text. This can be useful on web pages that display right-to-left test (like Arabic and Hebrew), but where the web pages don’t explicitly state the directionality.

Loading random images from the web can be problematic due to their size or content. By customizing shr-max-image-proportion you can set the maximal image proportion in relation to the window they are displayed in. E.g., 0.7 means an image is allowed to take up 70% of the width and height. If Emacs supports image scaling, then larger images are scaled down. You can block specific images completely by customizing shr-blocked-images.

You can control image display by customizing shr-inhibit-images. If this variable is nil, display the “ALT” text of images instead.

EWW (or rather its HTML renderer shr) uses the colors declared in the HTML page, but adjusts them if needed to keep a certain minimum contrast. If that is still too low for you, you can customize the variables shr-color-visible-distance-min and shr-color-visible-luminance-min to get a better contrast.

By default, the max width used when rendering is 120 characters, but this can be adjusted by changing the shr-max-width variable. If a specified width is preferred no matter what the width of the window is, shr-width can be set. If both variables are nil, the window width will always be used.

The HTML attribute aria-hidden is meant to tell screen readers to ignore a tag’s contents. You can customize the variable shr-discard-aria-hidden to tell shr to ignore such tags. This can be useful when using a screen reader on the output of shr (e.g., on EWW buffer text). It can be useful even when not using a screen reader, since web authors often put this attribute on non-essential decorative elements.

In addition to maintaining the history at run-time, EWW will also save the partial state of its buffers (the URIs and the titles of the pages visited) in the desktop file if one is used. See Saving Emacs Sessions in The GNU Emacs Manual.

EWW history may sensibly contain multiple entries for the same page URI. At run-time, these entries may still have different associated point positions or the actual Web page contents. The latter, however, tend to be overly large to preserve in the desktop file, so they get omitted, thus rendering the respective entries entirely equivalent. By default, such duplicate entries are not saved. Setting eww-desktop-remove-duplicates to nil will force EWW to save them anyway.

Restoring EWW buffers’ contents may prove to take too long to finish. When the eww-restore-desktop variable is set to nil (the default), EWW will not try to reload the last visited Web page when the buffer is restored from the desktop file, thus allowing for faster Emacs start-up times. When set to t, restoring the buffers will also initiate the reloading of such pages.

The EWW buffer restored from the desktop file but not yet reloaded will contain a prompt, as specified by the eww-restore-reload-prompt variable. The value of this variable will be passed through substitute-command-keys upon each use, thus allowing for the use of the usual substitutions, such as \[eww-reload] for the current key binding of the eww-reload command.

If the eww-auto-rename-buffer user option is non-nil, EWW buffers will be renamed after rendering a document. If this is title, rename based on the title of the document. If this is url, rename based on the URL of the document. This can also be a user-defined function, which is called with no parameters in the EWW buffer, and should return a string.

EWW runs the URLs through eww-url-transformers before using them. This user option is a list of functions, where each function is called with the URL as the parameter, and should return the (possibly) transformed URL. By default, this variable contains eww-remove-tracking, which removes the common ‘utm_’ trackers from links.

If Emacs has been built with xwidget support, EWW can use that to display ‘<video>’ elements. However, this support is still experimental, and on some systems doesn’t work (and even worse) may crash your Emacs, so this feature is off by default. If you wish to switch it on, set shr-use-xwidgets-for-media to a non-nil value.