Migrating to Slice Machine

I have a project that was created mostly without slices and as I understand it, even the slices I have are not the same format as the ones that work with Slice Machine.

Is there a guide for migrating to Slice Machine from the older format?
Is it possible to do this gradually?


Hello @seanl. Thanks for reaching out.
There is no official procedure or guide to migrate from the legacy builder to Slice Machine. We will give you a public announcement if this changes in the future.


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Hi Pau and Prismic Team

It has been 5 months since the last post in this thread. I run a design agencies's website as inhouse developer and would like to migrate from the legacy builder to slice machine. The reason i want to migrate is A. because the prismic documentation is all based on slice machine and B. because i love the shared slices aspect and that slices and custom types can be managed in the code.

Can you make a statement/estimate when a migration guide from legacy to slice machine will be published?

If i would know when there will be progress in the migration topic i could much better plan, how we will develop our website further this year. It makes a difference for our strategy/priorities if we go with legacy for another year or if we migrate to slice machine soon.

It would be really great to have a migration guide / info page which transparently informs what's possible already now and what is not possible yet. Currently the info seems to be scattered in the forum.

Thanks a lot : )

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Hello @yaay, thanks for sharing your comments.

At the moment, we don't have a universal solution as each use case is unique. For instance, some projects were initiated during the early stages of Slice Machine when both builders could coexist in a repository. Others have a toggle to select whether to work with the Legacy option or Slice Machine. Now, not all repositories have access to this option.

Right now you can only choose between Slice Machine or The Legacy Builder right when you create your repository.

Having a project with Legacy Builder and migrating it to Slice Machine may result in losing content due to potential conflicts with Slices' structure.

Therefore, we highly recommend that all our users begin using Slice Machine right from the start of their projects and continue using the Legacy Builder for their older projects.

We're continuously striving to enhance the user experience, but we don't have any updates yet regarding the release of a migration guide or tool. We understand the inconvenience this may cause and appreciate your patience.

Hi, I'm in a similar boat: old project (2018) with a lot of content that needs to be reworked - transition from React to Next.js - and wondering what to do.
Is it safe to keep developing older projects using the Legacy Builder? It won't ever be completely deprecated will it?

That's correct, @zvitez; we will not replace the Legacy Builder with Slice Machine. So you can continue using your past repositories without a problem.

Our current focus is aimed at supporting everything related to Slice Machine, the plugins to connect them with the most used frameworks, and all the functionality of the Builder in general. This means that anything related to the Legacy Builder will not have updates or new features from now on. We recommend that all our users use Slice Machine in their new projects.

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If Prismic is going all in on Slice Machine and if the Legacy builder is not going to receive any updates in the future, shouldn't it be a top priority to create a "single button migration tool" from legacy builder to slice machine?

80% of the Prismic websites I'm working with are using the Legacy builder and they will stay that indefinitely, because they don't want to spend a large sum of money to just migrate to Slice Machine (which is a tool for developers, so it's a very hard sell to the decision makers).

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The functionality of the Legacy Builder will remain stable. Therefore, projects that already exist should not worry about performing a migration. We still don't have an official tool or guide to migrate a project from Legacy Builder to Slice Machine.

Thanks for the confirmation. Slice Machine is an amazing tool and I'm happy to hear you're focusing on it.

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@Pau what is the update on that?
all your early clients are stuck with a deprecated tool, that's annoying :frowning:

Hey @sebastien.vassaux1, thanks for joining the conversation. We appreciate your interest. We want to let you know that our take on this matter remains the same as before:

Our team continually works to enhance the user experience, but we don't have any updates on when a migration guide or tool may be available. We understand that this may not be the answer you were hoping for, but please know that we are always here to support you if you have any other questions or concerns.

As I understand, we can't migrate from legacy builder to Slicemachine. And the legacy builder will no longer be updated, so it makes it impossible to scale or upgrade projects currently built on top of the legacy builder, right?

And looks like there are no plans to support migration because if you guys are working on for so long and there is no estimate to support this, makes it hard to believe it is going to happen someday.

I'm taking as an example prismic-javascript that is supposed to receive security updates but it doesn't.

This really put concerns about the current projects of my clients running on Prismic.

I really hope to before removing the legacy builder from the dashboard, have a full functional migration from it to slicemachine at least.

We can use the latest versions of prismic/client|react which are up to date. We just can't use the slice-machine. I've just updated a client project from years ago that used old versions of react to nextjs and everything works fine.

Just want to echo what @kris is saying here — early adopters of Prismic should have an easy and safe way to upgrade from Legacy Builder to Slice Machine. I’m frustrated that there is no upgrade path.

Maybe Prismic can give the open source community the tools they need to build this migration tool? I think there’s a lot of developers who would benefit from it.


Dear Prismic Team

Do you have any updates on future migration possibilities from legacy builder to slice machine?



Hi Everybody,

I want to reach out and let you know that we haven't this or our early adopters. We're considering numerous solutions for this at the moment and I'll get back to you in the following months with some of our plans for this.

That is to say, we're not working on anything yet and I'll not come back to you right away with a solution, but with how we plan to deliver on this.

Thanks for you patience. :slight_smile: