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Editorial Team
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Asked: 2026-05-20T20:30:18+00:00

So I’m trying to use a Rails URL helper ( page_url ) to create

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So I’m trying to use a Rails URL helper (page_url) to create URLs that contain special characters, including ampersands. Most cases work like you’d expect them to:

(rdb:1) page_url('foo', :host => 'host')
"http://host/pages/foo"
(rdb:1) page_url('foo_%_bar', :host => 'host')
"http://host/pages/foo_%25_bar"

But for some odd reason, ampersands are not escaped:

(rdb:1) page_url('foo_&_bar', :host => 'host')
"http://host/pages/foo_&_bar"

And if I pre-escape them, they get corrupted:

(rdb:1) page_url('foo_%26_bar', :host => 'host')
"http://host/pages/foo_%2526_bar"

CGI::escape, on the other hand, escapes them fine:

(rdb:1) CGI::escape('foo_&_bar')
"foo_%26_bar"

What’s going on, and how do I work around this? (With something nicer than gsub('&', '%26'), that is.)

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1 Answer

  1. Editorial Team

    I can’t tell you a nicer way to deal with it – but I can explain why it’s happening.

    Ampersands are not invalid characters for a URL. Otherwise you’d have problems with: “http://host/pages/foo?bar=baz&style=foo_style” or whatever.

    Edit:
    Digging deeper into the source code, it looks like Rails uses CGI.escape only on parameters.

    The helper, url-generators use url_for (under the covers), which eventually calls: http://apidock.com/rails/ActionController/Routing/Route/generate
    Which calls stuff deep in the sprivate-methods of the source code… but eventually ends up calling CGI.escape
    (first look in actionpack/lib/action_controller/routing/route.rb then in actionpack/lib/action_controller/routing/segments.rb )

    End result is that on the url itself, rails uses URI.escape – which notably does not update ampersands at all:

    >> CGI.escape('/my_foo_&_bar')
=> "%2Fmy_foo_%26_bar"
>> URI.escape('/my_foo_&_bar')
=> "/my_foo_&_bar"

    There’s currently nothing you can do about this without putting an actual feature-request onto the rails team.

    …unless you have the option to choose not to use ampersands in your URLs
    You can always gsub them out yourself for all URLs:

    def my_clean_url(the_url)
   return the_url.gsub(/&/,'_')
end
>> my_clean_url('/my_foo_&_bar')
=> "/my_foo___bar"

page_url(my_clean_url('/my_foo_&_bar'))
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