Prerendering: Viber support


I have enabled pre-rendering and it does not work on Viber.
Is Viber in the list of user-agents that will trigger pre-rendering?


Nope, never heard of that before and it is not in our list. What is Viber?

Sorry, I thought Viber is well known. It is a voice/text messenger like Telegram.

I hope you had time to evaluate Viber.

Is there any chance to add Viber in the list of supported user-agents?
If not, can I support Viber by using a custom prerender service (, self-hosted)?

Unfortunately, no, changing prerender service will not magically add new types to our detection. So - could you show me the docs where this application publishes its need for rendered content, as well as its stable User-Agent string, which will be how our CDN detects it? It is not obvious from reading the page that you linked that it needs such content, or what settings we might need to detect (we can only detect user agent :))

Thank you for considering to add Viber support!

I could not find any documentation either. I also searched in their development portal at I send them an email and I will inform you when/if they answer my request.

Before moving my sites to Netlify, I was using DigitalOcean and Dokku (Docker PaaS) with a self-hosted prerender instance. I used the user-agents for Viber, Viber Desktop and the previews were working but I understand that you need official docs for this.

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sounds great, jonian. Just circle back here if you get something official.

Hi again,

This is the response I got from Viber:

Hi Jonian,

When sharing links on Viber, the URL receives a request with the following user-agent:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_4) AppleWebKit/537.36 (KHTML, like Gecko) QtWebEngine/5.6.0 Chrome/45.0.2454.101 Safari/537.36 Viber

Let us know if this helps, or you need any additional information.

Hi, @jonian, well we wouldn’t want to trigger the prerender service for what might be a non-bot User-Agent. However, if the string “Viber” will always be present in these requests, we can trigger the prerender service based on the presence of that.

Does that sound acceptable to you?

Hi @luke, yes it is acceptable. Thank you for providing a solution so fast. You are awesome!

Hi, @jonian, it will take some time to actually get this change prepared and rolled out to our CDN. I’ll post another update here when that is complete.

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Hi, @jonian, the support for the Viber user-agent to trigger our prerendering service is now deployed to our ADN/CDN.

​Please let us know if there are any questions or more we can do to assist.

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Hi @luke, I tested it on Viber and Viber Desktop applications and it works! Thank you!