How long does it take to update Contact Lists API v1 to v3 in HubSpot?

[howardmarxb]

How many hours will a developer require to update our v1 Contact Lists API to v3?

Are there any developers interested in supporting us with this update?

[howardmarxb]

Hi @sylvain_tirreau,

Do you know of a developer who can help us migrate from v1 Contact List to v3?  Our back end is on Elixir and have a few API endpoints calling.

How many hours do you think this would take?

Thanks!

Best,
Howard

[BérangèreL]

Hi @howardmarxb and Happy Friday!
 

Thank you for reaching out to the HubSpot Community!
 

For information, the v1 Contact Lists API will be sunsetted on April 30, 2026.
 

To support your migration, you’ll need to update the three main endpoints you’re using to their v3 versions.

The migration guide offers clear endpoint mappings and practical examples to make the transition smoother.
 

Here are some helpful resources to get you started:

- List API migration guide
- Lists (Segments) API

I’m also looping in our fantastic Top Experts: Hi @sylvain_tirreau, @Anton and @Mike_Eastwood can you help @howardmarxb migrate from v1 Contact List to v3, please?

Or if you know any developers who might be interested in helping with this project, please let us know!

Thanks so much, and wishing everyone a wonderful weekend!
Bérangère

[howardmarxb]

Hi @Jaycee_Lewis ,

We currently have the following endpoints calling and our back-end is on Elixir.

Get all contacts GET /contacts/v1/lists/all/contacts/all
Get recently updated contacts: GET /contacts/v1/lists/recently_updated/contacts/recent
Get recently created contacts: GET /contacts/v1/lists/all/contacts/recent

Does anyone know approximately how many hours a developer would take to update these to v3?

We are not in a rush as HubSpot has its deadline on this forced update on April 30, 2026.

Thanks!
-Howard

[Jaycee_Lewis]

Hey, @howardmarxb 👋 That's a great question. My gut instinct is devs will need more specific details before they can give you a quote.

The complexity can vary a lot depending on how many lists you have and which specific V1 endpoints you're currently calling.

I'd suggest updating your post with the following details. This will help you get accurate hours and attract the right developer much faster:

• Scope — Which specific endpoints are you currently using, and how many lists are involved? What is the language/framework of your app that is using the API?
• Budget — Do you have a budget range in mind? .
• Timeframe — When do you require this completed? 

Thanks! — Jaycee