Action View Asset Tag Helpers

This module provides methods for generating HTML that links views to assets such as images, JavaScripts, stylesheets, and feeds. These methods do not verify the assets exist before linking to them:

image_tag("rails.png")
# => <img src="/assets/rails.png" />
stylesheet_link_tag("application")
# => <link href="/assets/application.css?body=1" rel="stylesheet" />

Methods

Included Modules

Instance Public methods

audio_tag(*sources)

Returns an HTML audio tag for the sources. If sources is a string, a single audio tag will be returned. If sources is an array, an audio tag with nested source tags for each source will be returned. The sources can be full paths, files that exist in your public audios directory, or Active Storage attachments.

When the last parameter is a hash you can add HTML attributes using that parameter.

audio_tag("sound")
# => <audio src="/audios/sound"></audio>
audio_tag("sound.wav")
# => <audio src="/audios/sound.wav"></audio>
audio_tag("sound.wav", autoplay: true, controls: true)
# => <audio autoplay="autoplay" controls="controls" src="/audios/sound.wav"></audio>
audio_tag("sound.wav", "sound.mid")
# => <audio><source src="/audios/sound.wav" /><source src="/audios/sound.mid" /></audio>

Active Storage blobs (audios that are uploaded by the users of your app):

audio_tag(user.name_pronunciation_audio)
# => <audio src="/rails/active_storage/blobs/.../name_pronunciation_audio.mp3"></audio>
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 593
      def audio_tag(*sources)
        multiple_sources_tag_builder("audio", sources)
      end
πŸ”Ž See on GitHub

Returns a link tag that browsers and feed readers can use to auto-detect an RSS, Atom, or JSON feed. The type can be :rss (default), :atom, or :json. Control the link options in url_for format using the url_options. You can modify the LINK tag itself in tag_options.

  • :rel - Specify the relation of this link, defaults to β€œalternate”

  • :type - Override the auto-generated mime type

  • :title - Specify the title of the link, defaults to the type

auto_discovery_link_tag
# => <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/action" />
auto_discovery_link_tag(:atom)
# => <link rel="alternate" type="application/atom+xml" title="ATOM" href="http://www.currenthost.com/controller/action" />
auto_discovery_link_tag(:json)
# => <link rel="alternate" type="application/json" title="JSON" href="http://www.currenthost.com/controller/action" />
auto_discovery_link_tag(:rss, {action: "feed"})
# => <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/controller/feed" />
auto_discovery_link_tag(:rss, {action: "feed"}, {title: "My RSS"})
# => <link rel="alternate" type="application/rss+xml" title="My RSS" href="http://www.currenthost.com/controller/feed" />
auto_discovery_link_tag(:rss, {controller: "news", action: "feed"})
# => <link rel="alternate" type="application/rss+xml" title="RSS" href="http://www.currenthost.com/news/feed" />
auto_discovery_link_tag(:rss, "http://www.example.com/feed.rss", {title: "Example RSS"})
# => <link rel="alternate" type="application/rss+xml" title="Example RSS" href="http://www.example.com/feed.rss" />
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 271
      def auto_discovery_link_tag(type = :rss, url_options = {}, tag_options = {})
        if !(type == :rss || type == :atom || type == :json) && tag_options[:type].blank?
          raise ArgumentError.new("You should pass :type tag_option key explicitly, because you have passed #{type} type other than :rss, :atom, or :json.")
        end

        tag(
          "link",
          "rel"   => tag_options[:rel] || "alternate",
          "type"  => tag_options[:type] || Template::Types[type].to_s,
          "title" => tag_options[:title] || type.to_s.upcase,
          "href"  => url_options.is_a?(Hash) ? url_for(url_options.merge(only_path: false)) : url_options
        )
      end
πŸ”Ž See on GitHub

Returns a link tag for a favicon managed by the asset pipeline.

If a page has no link like the one generated by this helper, browsers ask for /favicon.ico automatically, and cache the file if the request succeeds. If the favicon changes it is hard to get it updated.

To have better control applications may let the asset pipeline manage their favicon storing the file under app/assets/images, and using this helper to generate its corresponding link tag.

The helper gets the name of the favicon file as first argument, which defaults to β€œfavicon.ico”, and also supports :rel and :type options to override their defaults, β€œicon” and β€œimage/x-icon” respectively:

favicon_link_tag
# => <link href="/assets/favicon.ico" rel="icon" type="image/x-icon" />

favicon_link_tag 'myicon.ico'
# => <link href="/assets/myicon.ico" rel="icon" type="image/x-icon" />

Mobile Safari looks for a different link tag, pointing to an image that will be used if you add the page to the home screen of an iOS device. The following call would generate such a tag:

favicon_link_tag 'mb-icon.png', rel: 'apple-touch-icon', type: 'image/png'
# => <link href="/assets/mb-icon.png" rel="apple-touch-icon" type="image/png" />
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 312
      def favicon_link_tag(source = "favicon.ico", options = {})
        tag("link", {
          rel: "icon",
          type: "image/x-icon",
          href: path_to_image(source, skip_pipeline: options.delete(:skip_pipeline))
        }.merge!(options.symbolize_keys))
      end
πŸ”Ž See on GitHub

image_tag(source, options = {})

Returns an HTML image tag for the source. The source can be a full path, a file, or an Active Storage attachment.

Options

You can add HTML attributes using the options. The options supports additional keys for convenience and conformance:

  • :size - Supplied as "#{width}x#{height}" or "#{number}", so "30x45" becomes width="30" height="45", and "50" becomes width="50" height="50". :size will be ignored if the value is not in the correct format.

  • :srcset - If supplied as a hash or array of [source, descriptor] pairs, each image path will be expanded before the list is formatted as a string.

Examples

Assets (images that are part of your app):

image_tag("icon")
# => <img src="/assets/icon" />
image_tag("icon.png")
# => <img src="/assets/icon.png" />
image_tag("icon.png", size: "16x10", alt: "Edit Entry")
# => <img src="/assets/icon.png" width="16" height="10" alt="Edit Entry" />
image_tag("/icons/icon.gif", size: "16")
# => <img src="/icons/icon.gif" width="16" height="16" />
image_tag("/icons/icon.gif", height: '32', width: '32')
# => <img height="32" src="/icons/icon.gif" width="32" />
image_tag("/icons/icon.gif", class: "menu_icon")
# => <img class="menu_icon" src="/icons/icon.gif" />
image_tag("/icons/icon.gif", data: { title: 'Rails Application' })
# => <img data-title="Rails Application" src="/icons/icon.gif" />
image_tag("icon.png", srcset: { "icon_2x.png" => "2x", "icon_4x.png" => "4x" })
# => <img src="/assets/icon.png" srcset="/assets/icon_2x.png 2x, /assets/icon_4x.png 4x">
image_tag("pic.jpg", srcset: [["pic_1024.jpg", "1024w"], ["pic_1980.jpg", "1980w"]], sizes: "100vw")
# => <img src="/assets/pic.jpg" srcset="/assets/pic_1024.jpg 1024w, /assets/pic_1980.jpg 1980w" sizes="100vw">

Active Storage blobs (images that are uploaded by the users of your app):

image_tag(user.avatar)
# => <img src="/rails/active_storage/blobs/.../tiger.jpg" />
image_tag(user.avatar.variant(resize_to_limit: [100, 100]))
# => <img src="/rails/active_storage/representations/.../tiger.jpg" />
image_tag(user.avatar.variant(resize_to_limit: [100, 100]), size: '100')
# => <img width="100" height="100" src="/rails/active_storage/representations/.../tiger.jpg" />
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 430
      def image_tag(source, options = {})
        options = options.symbolize_keys
        check_for_image_tag_errors(options)
        skip_pipeline = options.delete(:skip_pipeline)

        options[:src] = resolve_asset_source("image", source, skip_pipeline)

        if options[:srcset] && !options[:srcset].is_a?(String)
          options[:srcset] = options[:srcset].map do |src_path, size|
            src_path = path_to_image(src_path, skip_pipeline: skip_pipeline)
            "#{src_path} #{size}"
          end.join(", ")
        end

        options[:width], options[:height] = extract_dimensions(options.delete(:size)) if options[:size]

        options[:loading] ||= image_loading if image_loading
        options[:decoding] ||= image_decoding if image_decoding

        tag("img", options)
      end
πŸ”Ž See on GitHub

javascript_include_tag(*sources)

Returns an HTML script tag for each of the sources provided.

Sources may be paths to JavaScript files. Relative paths are assumed to be relative to assets/javascripts, full paths are assumed to be relative to the document root. Relative paths are idiomatic, use absolute paths only when needed.

When passing paths, the β€œ.js” extension is optional. If you do not want β€œ.js” appended to the path extname: false can be set on the options.

You can modify the HTML attributes of the script tag by passing a hash as the last argument.

When the Asset Pipeline is enabled, you can pass the name of your manifest as source, and include other JavaScript or CoffeeScript files inside the manifest.

If the server supports HTTP Early Hints, and the defer option is not enabled, Rails will push a 103 Early Hints response that links to the assets.

Options

When the last parameter is a hash you can add HTML attributes using that parameter. This includes but is not limited to the following options:

  • :extname - Append an extension to the generated URL unless the extension already exists. This only applies for relative URLs.

  • :protocol - Sets the protocol of the generated URL. This option only applies when a relative URL and host options are provided.

  • :host - When a relative URL is provided the host is added to the that path.

  • :skip_pipeline - This option is used to bypass the asset pipeline when it is set to true.

  • :nonce - When set to true, adds an automatic nonce value if you have Content Security Policy enabled.

  • :async - When set to true, adds the async HTML attribute, allowing the script to be fetched in parallel to be parsed and evaluated as soon as possible.

  • :defer - When set to true, adds the defer HTML attribute, which indicates to the browser that the script is meant to be executed after the document has been parsed. Additionally, prevents sending the Preload Links header.

  • :nopush - Specify if the use of server push is not desired for the script. Defaults to true.

Any other specified options will be treated as HTML attributes for the script tag.

For more information regarding how the :async and :defer options affect the <script> tag, please refer to the MDN docs.

Examples

javascript_include_tag "xmlhr"
# => <script src="/assets/xmlhr.debug-1284139606.js"></script>

javascript_include_tag "xmlhr", host: "localhost", protocol: "https"
# => <script src="https://localhost/assets/xmlhr.debug-1284139606.js"></script>

javascript_include_tag "template.jst", extname: false
# => <script src="/assets/template.debug-1284139606.jst"></script>

javascript_include_tag "xmlhr.js"
# => <script src="/assets/xmlhr.debug-1284139606.js"></script>

javascript_include_tag "common.javascript", "/elsewhere/cools"
# => <script src="/assets/common.javascript.debug-1284139606.js"></script>
#    <script src="/elsewhere/cools.debug-1284139606.js"></script>

javascript_include_tag "http://www.example.com/xmlhr"
# => <script src="http://www.example.com/xmlhr"></script>

javascript_include_tag "http://www.example.com/xmlhr.js"
# => <script src="http://www.example.com/xmlhr.js"></script>

javascript_include_tag "http://www.example.com/xmlhr.js", nonce: true
# => <script src="http://www.example.com/xmlhr.js" nonce="..."></script>

javascript_include_tag "http://www.example.com/xmlhr.js", async: true
# => <script src="http://www.example.com/xmlhr.js" async="async"></script>

javascript_include_tag "http://www.example.com/xmlhr.js", defer: true
# => <script src="http://www.example.com/xmlhr.js" defer="defer"></script>
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 113
      def javascript_include_tag(*sources)
        options = sources.extract_options!.stringify_keys
        path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
        preload_links = []
        use_preload_links_header = options["preload_links_header"].nil? ? preload_links_header : options.delete("preload_links_header")
        nopush = options["nopush"].nil? ? true : options.delete("nopush")
        crossorigin = options.delete("crossorigin")
        crossorigin = "anonymous" if crossorigin == true
        integrity = options["integrity"]
        rel = options["type"] == "module" ? "modulepreload" : "preload"

        sources_tags = sources.uniq.map { |source|
          href = path_to_javascript(source, path_options)
          if use_preload_links_header && !options["defer"] && href.present? && !href.start_with?("data:")
            preload_link = "<#{href}>; rel=#{rel}; as=script"
            preload_link += "; crossorigin=#{crossorigin}" unless crossorigin.nil?
            preload_link += "; integrity=#{integrity}" unless integrity.nil?
            preload_link += "; nopush" if nopush
            preload_links << preload_link
          end
          tag_options = {
            "src" => href,
            "crossorigin" => crossorigin
          }.merge!(options)
          if tag_options["nonce"] == true
            tag_options["nonce"] = content_security_policy_nonce
          end
          content_tag("script", "", tag_options)
        }.join("\n").html_safe

        if use_preload_links_header
          send_preload_links_header(preload_links)
        end

        sources_tags
      end
πŸ”Ž See on GitHub

picture_tag(*sources, &block)

Returns an HTML picture tag for the sources. If sources is a string, a single picture tag will be returned. If sources is an array, a picture tag with nested source tags for each source will be returned. The sources can be full paths, files that exist in your public images directory, or Active Storage attachments. Since the picture tag requires an img tag, the last element you provide will be used for the img tag. For complete control over the picture tag, a block can be passed, which will populate the contents of the tag accordingly.

Options

When the last parameter is a hash you can add HTML attributes using that parameter. Apart from all the HTML supported options, the following are supported:

  • :image - Hash of options that are passed directly to the image_tag helper.

Examples

picture_tag("picture.webp")
# => <picture><img src="/images/picture.webp" /></picture>
picture_tag("gold.png", :image => { :size => "20" })
# => <picture><img height="20" src="/images/gold.png" width="20" /></picture>
picture_tag("gold.png", :image => { :size => "45x70" })
# => <picture><img height="70" src="/images/gold.png" width="45" /></picture>
picture_tag("picture.webp", "picture.png")
# => <picture><source srcset="/images/picture.webp" /><source srcset="/images/picture.png" /><img src="/images/picture.png" /></picture>
picture_tag("picture.webp", "picture.png", :image => { alt: "Image" })
# => <picture><source srcset="/images/picture.webp" /><source srcset="/images/picture.png" /><img alt="Image" src="/images/picture.png" /></picture>
picture_tag(["picture.webp", "picture.png"], :image => { alt: "Image" })
# => <picture><source srcset="/images/picture.webp" /><source srcset="/images/picture.png" /><img alt="Image" src="/images/picture.png" /></picture>
picture_tag(:class => "my-class") { tag(:source, :srcset => image_path("picture.webp")) + image_tag("picture.png", :alt => "Image") }
# => <picture class="my-class"><source srcset="/images/picture.webp" /><img alt="Image" src="/images/picture.png" /></picture>
picture_tag { tag(:source, :srcset => image_path("picture-small.webp"), :media => "(min-width: 600px)") + tag(:source, :srcset => image_path("picture-big.webp")) + image_tag("picture.png", :alt => "Image") }
# => <picture><source srcset="/images/picture-small.webp" media="(min-width: 600px)" /><source srcset="/images/picture-big.webp" /><img alt="Image" src="/images/picture.png" /></picture>

Active Storage blobs (images that are uploaded by the users of your app):

picture_tag(user.profile_picture)
# => <picture><img src="/rails/active_storage/blobs/.../profile_picture.webp" /></picture>
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 491
      def picture_tag(*sources, &block)
        sources.flatten!
        options = sources.extract_options!.symbolize_keys
        image_options = options.delete(:image) || {}
        skip_pipeline = options.delete(:skip_pipeline)

        content_tag("picture", options) do
          if block.present?
            capture(&block).html_safe
          elsif sources.size <= 1
            image_tag(sources.last, image_options)
          else
            source_tags = sources.map do |source|
              tag("source",
               srcset: resolve_asset_source("image", source, skip_pipeline),
               type: Template::Types[File.extname(source)[1..]]&.to_s)
            end
            safe_join(source_tags << image_tag(sources.last, image_options))
          end
        end
      end
πŸ”Ž See on GitHub

Returns a link tag that browsers can use to preload the source. The source can be the path of a resource managed by asset pipeline, a full path, or an URI.

  • :type - Override the auto-generated mime type, defaults to the mime type for source extension.

  • :as - Override the auto-generated value for as attribute, calculated using source extension and mime type.

  • :crossorigin - Specify the crossorigin attribute, required to load cross-origin resources.

  • :nopush - Specify if the use of server push is not desired for the resource. Defaults to false.

  • :integrity - Specify the integrity attribute.

preload_link_tag("custom_theme.css")
# => <link rel="preload" href="/assets/custom_theme.css" as="style" type="text/css" />

preload_link_tag("/videos/video.webm")
# => <link rel="preload" href="/videos/video.mp4" as="video" type="video/webm" />

preload_link_tag(post_path(format: :json), as: "fetch")
# => <link rel="preload" href="/posts.json" as="fetch" type="application/json" />

preload_link_tag("worker.js", as: "worker")
# => <link rel="preload" href="/assets/worker.js" as="worker" type="text/javascript" />

preload_link_tag("//example.com/font.woff2")
# => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="anonymous"/>

preload_link_tag("//example.com/font.woff2", crossorigin: "use-credentials")
# => <link rel="preload" href="//example.com/font.woff2" as="font" type="font/woff2" crossorigin="use-credentials" />

preload_link_tag("/media/audio.ogg", nopush: true)
# => <link rel="preload" href="/media/audio.ogg" as="audio" type="audio/ogg" />
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 355
      def preload_link_tag(source, options = {})
        href = path_to_asset(source, skip_pipeline: options.delete(:skip_pipeline))
        extname = File.extname(source).downcase.delete(".")
        mime_type = options.delete(:type) || Template::Types[extname]&.to_s
        as_type = options.delete(:as) || resolve_link_as(extname, mime_type)
        crossorigin = options.delete(:crossorigin)
        crossorigin = "anonymous" if crossorigin == true || (crossorigin.blank? && as_type == "font")
        integrity = options[:integrity]
        nopush = options.delete(:nopush) || false
        rel = mime_type == "module" ? "modulepreload" : "preload"

        link_tag = tag.link(
          rel: rel,
          href: href,
          as: as_type,
          type: mime_type,
          crossorigin: crossorigin,
          **options.symbolize_keys)

        preload_link = "<#{href}>; rel=#{rel}; as=#{as_type}"
        preload_link += "; type=#{mime_type}" if mime_type
        preload_link += "; crossorigin=#{crossorigin}" if crossorigin
        preload_link += "; integrity=#{integrity}" if integrity
        preload_link += "; nopush" if nopush

        send_preload_links_header([preload_link])

        link_tag
      end
πŸ”Ž See on GitHub

Returns a stylesheet link tag for the sources specified as arguments.

When passing paths, the .css extension is optional. If you don’t specify an extension, .css will be appended automatically. If you do not want .css appended to the path, set extname: false in the options. You can modify the link attributes by passing a hash as the last argument.

If the server supports HTTP Early Hints, Rails will push a 103 Early Hints response that links to the assets.

  • :extname - Append an extension to the generated URL unless the extension already exists. This only applies for relative URLs.

  • :protocol - Sets the protocol of the generated URL. This option only applies when a relative URL and host options are provided.

  • :host - When a relative URL is provided the host is added to the that path.

  • :skip_pipeline - This option is used to bypass the asset pipeline when it is set to true.

  • :nonce - When set to true, adds an automatic nonce value if you have Content Security Policy enabled.

  • :nopush - Specify if the use of server push is not desired for the stylesheet. Defaults to true.

stylesheet_link_tag "style"
# => <link href="/assets/style.css" rel="stylesheet" />

stylesheet_link_tag "style.css"
# => <link href="/assets/style.css" rel="stylesheet" />

stylesheet_link_tag "http://www.example.com/style.css"
# => <link href="http://www.example.com/style.css" rel="stylesheet" />

stylesheet_link_tag "style.less", extname: false, skip_pipeline: true, rel: "stylesheet/less"
# => <link href="/stylesheets/style.less" rel="stylesheet/less">

stylesheet_link_tag "style", media: "all"
# => <link href="/assets/style.css" media="all" rel="stylesheet" />

stylesheet_link_tag "style", media: "print"
# => <link href="/assets/style.css" media="print" rel="stylesheet" />

stylesheet_link_tag "random.styles", "/css/stylish"
# => <link href="/assets/random.styles" rel="stylesheet" />
#    <link href="/css/stylish.css" rel="stylesheet" />

stylesheet_link_tag "style", nonce: true
# => <link href="/assets/style.css" rel="stylesheet" nonce="..." />
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 202
      def stylesheet_link_tag(*sources)
        options = sources.extract_options!.stringify_keys
        path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
        use_preload_links_header = options["preload_links_header"].nil? ? preload_links_header : options.delete("preload_links_header")
        preload_links = []
        crossorigin = options.delete("crossorigin")
        crossorigin = "anonymous" if crossorigin == true
        nopush = options["nopush"].nil? ? true : options.delete("nopush")
        integrity = options["integrity"]

        sources_tags = sources.uniq.map { |source|
          href = path_to_stylesheet(source, path_options)
          if use_preload_links_header && href.present? && !href.start_with?("data:")
            preload_link = "<#{href}>; rel=preload; as=style"
            preload_link += "; crossorigin=#{crossorigin}" unless crossorigin.nil?
            preload_link += "; integrity=#{integrity}" unless integrity.nil?
            preload_link += "; nopush" if nopush
            preload_links << preload_link
          end
          tag_options = {
            "rel" => "stylesheet",
            "crossorigin" => crossorigin,
            "href" => href
          }.merge!(options)
          if tag_options["nonce"] == true
            tag_options["nonce"] = content_security_policy_nonce
          end

          if apply_stylesheet_media_default && tag_options["media"].blank?
            tag_options["media"] = "screen"
          end

          tag(:link, tag_options)
        }.join("\n").html_safe

        if use_preload_links_header
          send_preload_links_header(preload_links)
        end

        sources_tags
      end
πŸ”Ž See on GitHub

video_tag(*sources)

Returns an HTML video tag for the sources. If sources is a string, a single video tag will be returned. If sources is an array, a video tag with nested source tags for each source will be returned. The sources can be full paths, files that exist in your public videos directory, or Active Storage attachments.

Options

When the last parameter is a hash you can add HTML attributes using that parameter. The following options are supported:

  • :poster - Set an image (like a screenshot) to be shown before the video loads. The path is calculated like the src of image_tag.

  • :size - Supplied as "#{width}x#{height}" or "#{number}", so "30x45" becomes width="30" height="45", and "50" becomes width="50" height="50". :size will be ignored if the value is not in the correct format.

  • :poster_skip_pipeline will bypass the asset pipeline when using the :poster option instead using an asset in the public folder.

Examples

video_tag("trailer")
# => <video src="/videos/trailer"></video>
video_tag("trailer.ogg")
# => <video src="/videos/trailer.ogg"></video>
video_tag("trailer.ogg", controls: true, preload: 'none')
# => <video preload="none" controls="controls" src="/videos/trailer.ogg"></video>
video_tag("trailer.m4v", size: "16x10", poster: "screenshot.png")
# => <video src="/videos/trailer.m4v" width="16" height="10" poster="/assets/screenshot.png"></video>
video_tag("trailer.m4v", size: "16x10", poster: "screenshot.png", poster_skip_pipeline: true)
# => <video src="/videos/trailer.m4v" width="16" height="10" poster="screenshot.png"></video>
video_tag("/trailers/hd.avi", size: "16x16")
# => <video src="/trailers/hd.avi" width="16" height="16"></video>
video_tag("/trailers/hd.avi", size: "16")
# => <video height="16" src="/trailers/hd.avi" width="16"></video>
video_tag("/trailers/hd.avi", height: '32', width: '32')
# => <video height="32" src="/trailers/hd.avi" width="32"></video>
video_tag("trailer.ogg", "trailer.flv")
# => <video><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>
video_tag(["trailer.ogg", "trailer.flv"])
# => <video><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>
video_tag(["trailer.ogg", "trailer.flv"], size: "160x120")
# => <video height="120" width="160"><source src="/videos/trailer.ogg" /><source src="/videos/trailer.flv" /></video>

Active Storage blobs (videos that are uploaded by the users of your app):

video_tag(user.intro_video)
# => <video src="/rails/active_storage/blobs/.../intro_video.mp4"></video>
πŸ“ Source code 
# File actionview/lib/action_view/helpers/asset_tag_helper.rb, line 561
      def video_tag(*sources)
        options = sources.extract_options!.symbolize_keys
        public_poster_folder = options.delete(:poster_skip_pipeline)
        sources << options
        multiple_sources_tag_builder("video", sources) do |tag_options|
          tag_options[:poster] = path_to_image(tag_options[:poster], skip_pipeline: public_poster_folder) if tag_options[:poster]
          tag_options[:width], tag_options[:height] = extract_dimensions(tag_options.delete(:size)) if tag_options[:size]
        end
      end
πŸ”Ž See on GitHub