Toolbar Preview cookie issue

Hi Fares,

Sure, here's the screenshot of my cookies on local and production site, with io.prismic.preview highlight:

Hope that helps. I'll be following the issue via the link you're sharing too.

Let me know if you need any else info. Thanks!

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Adding some additional context here for reference.

  1. I recently created a new repo and used the same stack to reference prismic as my older repos, the new repo works as expected for previewing content. So, this preview issue only seems to occur on older repos, possibly the ones that were migrated from the previous version of the toolbar.

  2. When inspecting the cookies between the two repos/sites, I'm not seeing "io.prismic.previewSession" in the older repo which the preview functionality is not working.

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Hello @Fares @Phil,

this issue has been openned for more than 10 days now, and at this time we have no visibility on its resolving status.
As it is an everyday feature used by our integration team, we are really concerned regarding this.
Could you give us updates on this resolving ?
Do you have any idea how long the fix will take to be deployed ?
Any idea of a workaround ?


Hi Vivien,

We apologise for the delay, our dev team are still investigating the issue and for some users we are suspecting this issue:

A cookie associated with a cross-site resource at was set without the `SameSite` attribute. It has been blocked, as Chrome now only delivers cookies with cross-site requests if they are set with `SameSite=None` and `Secure`. You can review cookies in developer tools under Application>Storage>Cookies and see more details at and

Meaning that if that is the issue then it can be due to a change on chrome side that will require some changes of the way we create preview cookies.

But we are still investigating the issue that the other users having, and we let know if have any updates.

Hi there,

I tested the preview this morning. And out of nothing it works again for me. Did not change anything regarding the preview.
So I am happy that it works again. But it's a pity to not know why, or what the problem was.

Cheers and good luck with the further investigations :slight_smile:


we are experiencing the same problem on Firefox, so I don't think it is a Chrome side issue.
And for the record, we have a problem on one repo, on the other repo it works fine.
But thanks for the update :slight_smile:

I have 3 different repos with this problem occurring.
Using v4, nothing loads on localhost:8000
On live URLs I'm getting constant refreshing. Which is slightly different to what i had before which was just a blank page.

I'm also experiencing this issue on a SvelteKit site in which Prismic was implemented following the Javascript documentation. It's not working in either Chrome or Safari on Mac.

Same issue here. All I can add is that old browser sessions with a cookie still work but starting a new preview in incognito doesn't generate the io.prismic.preview cookie.

Hi there,

May I have the repository name with the issue (in a private message if necessary)?

We are still investigating the issue and we have narrowed down the cause to a few possibilities, we need to gather some impacted repositories to test the proposed fix.

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So we've identified the issue and are working on resolving the problem. We will update you once this is done.

Thank you for your patience and understanding.


We've deployed a fix and we are now adding it to all your repositories. We'll let you know when this is done. If you haven't done so yet, please share your repo URL so we can make sure we deploy the fix for you. :slight_smile:

Great, thanks. I DM'd you just in case. Are you able to give us a bit more info of what caused the bug for the more curious among us?

We introduced a change in the way we manage sessions a few weeks ago that prevented the preview session to be triggered properly. This was done as part of more important work to improve the login experience.

The progressive deployment is explaining why some people faced the issue in a progressive way and not all at once.

Thanks for the info, useful to know


A fix for this issue has been implemented and deployed for all clients, can you please let me know if It still doesn't work for you to further troubleshoot.

This thread has been closed due to inactivity. Flag to reopen.