Do you want to only validate the format or that the url really exists and returns something?

For now the url format is my only concern.

There is validate_format/4 where you can write a regexp for url validation, or something like this EctoFields.URL

So if I get it right, for some specific url I can combine validate_format/4 and EctoFields.URL.

Edit: If I don’t want to write some long regex like http://www\.youtube\.com\/(.+)|https://www\.youtube\.com\/(.+). ^^

Then something like this https://stackoverflow.com/questions/39041335/how-to-validate-url-in-elixir

If you want to validate a specific format for YouTube, then I think you will have to write a regexp for YouTube and handle different cases.

http://www\.youtube\.com\/(.+)|https://www\.youtube\.com\/(.+) is of course not so optimal. Could be done with http(s)?:\/\/www\.youtube\.com\/(.+).

Maybe also see this topic for inspiration Validating youtube link

I have a small lib called ex_url that parses URLs that you might find helpful.

Thanks to all the suggestions, finally I managed to write a really naive module for my url validation with Ecto.

My use case is very simple. In my project I want users to add their personal website url or their social link (facebook, twitter, etc.).

• for some personal website any valid url is okay.
• for some social link I need to ensure that the said social network name is included in a valid url.

All that validations are just for users browsing convenience. I won’t do anything with the urls apart displaying them on the owner profile page.

I choose the regex solution suggested by @egze because like that I won’t have to add any extra dependency to my project. Thanks also to @wolfiton that provided to me links to great resources on regex writing.

So see below a sample of the module

defmodule Easy.Url do
  @moduledoc """
  A module for url validation with Ecto
  """

  alias Ecto.{Changeset}
  import Changeset, only: [validate_format: 3]

  @before_tld "^(((ht|f)tp(s?))\://)?(www.|[a-zA-Z].)[a-zA-Z0-9\-\.]"
  @tld "([a-zA-Z])"
  @after_tld "(\:[0-9]+)*(/($|[a-zA-Z0-9\.\,\;\?\'\\\+&%\$#\=~_\-]+))*$"

  @regex Regex.compile!("#{@before_tld}+\.#{@tld}#{@after_tld}")

  @doc """
  Validate an url
  """
  def validate_url(changeset, field), do: validate_format(changeset, field, @regex)

  @doc """
  Validate an url for only some given top level domains
  """
  def validate_url(changeset, field, tld_list) do
    tld = Enum.join(tld_list, "|")

    case Regex.compile("#{@before_tld}+\.#{tld}#{@after_tld}") do
      {:ok, regex} ->
        validate_format(changeset, field, regex)

      _ ->
        validate_url(changeset, field)
    end
  end

  @doc """
  Validate an url while ensuring it contains a given domain
  """
  def validate_specific_url(changeset, field, domain) do
    changeset
    |> validate_url(field)
    |> validate_format(field, ~r/#{domain}/)
  end
end

Edit: Any suggestion is welcome of course.

Unfortunately your regex won’t parse some valid URLs like:

iex> Regex.match? @regex, "https://user:pass@my_site.com"          
false
iex> Regex.match? @regex, "https://my_site.com?tracking_token=some_token"   
false
iex> Regex.match? @regex, "https://my_site.com/" 

All of which can be parsed by the built-in URI module (ie no new dependency). For example:

iex> URI.parse "https://user:pass@my_site.com/"       
%URI{
  authority: "user:pass@my_site.com",
  fragment: nil,
  host: "my_site.com",
  path: "/",
  port: 443,
  query: nil,
  scheme: "https",
  userinfo: "user:pass"
}