Task ID returned from the API has changed?

Materials Project
1

Hi, task ID returned in JSON is only letters now, instead of numbers:

{"data": [{"formula_pretty": "Fe2O3", "material_id": "mp-aaaaacea",

When copied in the browser it redirects to the numerical ID:

https://next-gen.materialsproject.org/materials/mp-aaaaacea

mp-1456. Is it intentional? Can we get back numerical IDs?

Thanks.

2

Hi Sasha,

This was an intentional change made in our database release v2026.04.13. This decision was made primarily because the Material and Task ID namespaces were becoming increasingly conflated - moving Materials to AlphaID creates a clear distinction between the two. Additionally, AlphaIDs are sortable, more memorable, and more easily extensible as identifiers.

To convert between the AlphaID (new format) and the Numeric ID (old format), it’s a base conversion from base-26 to base-10.

You can read more about this in our documentation.

3

Thanks for a fast reply, very helpful.

1 Like
4

Some feedback from our users. They don’t like it =)

Couple of reasons:

  1. Website itself and google still has numerical IDs (google Si) will get get URL with mp-149
  2. Alphanumeric IDs are the same length so it is harder to spot things.

Will try to alleviate by providing also the old one (by conversion from base-26 to base-10). Since you mentioned it is extensible, it is now clear to me that it will work in the future (if this is guaranteed).

Thanks, Sasha.

5

Hi @sasha,

Will just point you to here for a longer post I made on the subject for more details: Updates to Identifier Systems in the Materials Project

For #1 about urls + website: See the numbered list in that post and the bit that starts with Translating the comparisons above into URLs/queries:
TLDR is the backend will accept any id format you pass, even mixed formats, so URLs, Google search results, DOIs, etc. will always still resolve. The website also has user a profile option in the Dashboard to change how IDs are displayed across the website.

For #2 the REST API accepts an additional query parameter id_format to have the IDs formatted directly in the response from the server, see the final footer marked ***. Probably the most relevant for you as a dev.

This option hasn’t propagated to the mp-api client yet in a documented way. It can be passed as a kwarg to the internal _search function, but it’s not very ergonomic

>>> mpr = MPRester(use_document_model=False)
>>> mpr.materials.summary._search(
    material_ids=["mp-149"],
    fields=["material_id", "task_ids"],
    id_format="legacy"
)
[{'material_id': 'mp-149', 'task_ids': ['mp-2629357', 'mp-2064724', ...]}]

On the todo list for the next release of mp-api

6

This is great, thanks! I tried and it works, we are actually using requests directly, so no need to wait for mp-api.

1 Like
7

That’s great, glad to hear it :slight_smile: