UrlField.max_length is too short

Wagtail is using the UrlField provided by Django, which has max_length=200. Sometimes this is not enough, especially for certain embeds.

Could we use a value larger than that for maybe all UrlFields in Wagtail? Or what would be the best way to override this on a specific website?

Related to this, someone managed to submit a page with a long url without any validation errors, which then failed when publishing it. But the draft did get saved (along with the long url) but the page editor form didn’t render at all (because of an error when rendering the url field and TEMPLATE_DEBUG=False). Changing the embed url field length directly in the database fixed this. Although this was an older version of Wagtail, so I’ll give it a try on 1.2 with richtext embeds and streamfield embed blocks too.

[GTpyro]

Instagram embed doesn’t work either, due to thumbnail_urls that are too long such as:

https://instagram.fauh1-1.fna.fbcdn.net/v/t51.2885-15/sh0.08/e35/s640x640/81212482_896587687411263_2564978143874747214_n.jpg?_nc_ht=instagram.fauh1-1.fna.fbcdn.net&_nc_cat=103&_nc_ohc=mr0u0N1_U28AX-b_92X&oh=bedb12c1cd591f8570e0833c33d0c24e&oe=5EA87F75

Seeing as this problem is caused by this bug, instead of creating a new issue, I’m just reporting it here, hope that’s alright.

I just ran into this exact problem and my google skills failed me before I opened up #6467. It’s essentially the same issue. The max_length constraint is currently preventing me from embedding instagram posts.

[thibaudcolas]

See also #4292:

Embedding a URL longer than 200 chars results in: DataError: value too long for type character varying(200).

Steps to Reproduce

1. In a Wagtail project using StreamField
2. Add ('embed', EmbedBlock()), to it
3. Create/edit a page and add an Embed block
4. Add an URL with more than 200 chars (for example: https://youtu.be/YBpdL9hSac4?module=Widgetize&action=iframe&containerId=VisitOverviewWithGraph&widget=1&moduleToWidgetize=CoreHome&actionToWidgetize=renderWidgetContainer&idSite=1&period=day&date=today&disableLink=1&widget=1

From wagtail/embeds/models.py#L23 (url = models.URLField()) url is being created with a default max_length of 200. We should be able to safely increase this limit to max_length=255. I may still run into issues with Matomo URLs but I can’t think of a reason to not allow 255 chars. More would give me more breathing room but that can potentially cause issues with some (older) backends, MySQL < 5.0.3 comes to mind.

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In my opinion there shouldn’t be any length restriction on embed URLs. I don’t see the value in having that restriction to start with, and in many cases shortening the URL to make it comply simply isn’t an option.