Anyway to allow shared emails?

I have a multi-tenant setup, with an extra column "project_id" setup in my schema, with my database itself confining emails to be unique to projects.

Is there any config value I can change to allow sign-ups with existing emails? No matter what I try (so far), I get the error "Sign-up attempt for existing email: ...."

PPlaton I have a multi-tenant setup, with an extra column "project_id" setup in my schem...

Ping•4/17/25, 1:40 PM

Better Auth email & password auth doesn't allow emails that already exist to sign-up, and it's not configurable. You may want to re-think the project system, as it probably wont work-out using BA unfortunately.

PlatonOP•4/17/25, 1:42 PM

Is it worth me putting a feature request in, or is that something that's never going to change?

This would almost instantly allow for multi-tenant setups

PlatonOP•4/17/25, 1:43 PM

Alternatively, maybe a custom plugin would solve this?

PPlaton Is it worth me putting a feature request in, or is that something that's never g...

Ping•4/17/25, 1:45 PM

Most people would be using an organization plugin for project structure systems.

Ping•4/17/25, 1:47 PM

You can configure orgs to be per-email if you want

PlatonOP•4/17/25, 1:47 PM

True, organisations are applicable for most use-cases, but this is another layer of grouping on top of that

PPlaton True, organisations are applicable for most use-cases, but this is another layer...

Ping•4/17/25, 1:48 PM

Can I know your goal?

PlatonOP•4/17/25, 1:49 PM

We've got a b2b2b setup, where:

company registers with us, and has a dashboard created for them and their domain
company sells to customers, so all of those customers are only expected to be unique for that dashboard

PlatonOP•4/17/25, 1:50 PM

With emails being enforced to be unique across the entire system, a customer can't have an account on dashboard A, and dashboard B at the same time

PlatonOP•4/17/25, 1:51 PM

Any kinda b2b2b setup will operate the same way, think of any setup where a company offers a reseller service for example

PlatonOP•4/17/25, 1:53 PM

If you can't support this, I can get around this by adding another column to store their real emails, and just setting the original email column to {uuid}@test.com, but that's hacky and means I can't use your pre-built email tools

PlatonOP•4/17/25, 1:54 PM

But honestly, this is by far better than alternatives so I'll do it if I can't figure out another solution here haha

PlatonOP•4/17/25, 1:54 PM

By alternatives I mean authjs etc

PlatonOP•4/17/25, 2:25 PM

Alternatively, allow us to override field values with things we can do with additionalFields, rather than just changing the key of the field

Ping•4/17/25, 2:30 PM

I believe I understand your goal now - and yeah, for sure at another layer above what BA offers.

Just curious, how would signing in work? We'd just check the user's email against every matching email and find a password that matches what they inputted? What happens if both accounts used the same password?

PlatonOP•4/17/25, 2:30 PM

https://github.com/better-auth/better-auth/issues/1248

Just found an existing issue which seems related

GitHub

Multi-Tenant userbases / updatable user schema · Issue #1248 · be...

Is this suited for github? Yes, this is suited for github Is your feature request related to a problem? Please describe. Hi, I'm looking to create a B2B2C SaaS application with a couple require...

PlatonOP•4/17/25, 2:31 PM

So either the client or server needs to know the tenant

PlatonOP•4/17/25, 2:32 PM

With our system, we look at the host to find a tenant, and then based on that we look at all users that are under that tenant to see if the user exists

PlatonOP•4/17/25, 2:32 PM

So it would have to work async somehow

PlatonOP•4/17/25, 2:32 PM

It doesn't care about the password at this stage

Ping•4/17/25, 2:33 PM

Would this work for your case?

PlatonOP•4/17/25, 2:33 PM

Yeah that would work, it just means we can't use your email tools like signup/user profile change notifications

PlatonOP•4/17/25, 2:34 PM

Thats the only drawback :/

PPlaton Yeah that would work, it just means we can't use your email tools like signup/us...

Ping•4/17/25, 2:34 PM

are you referring to useSession? What do you mean profile change notification?

PlatonOP•4/17/25, 2:35 PM

https://www.better-auth.com/docs/concepts/email

Email | Better Auth

Learn how to use email with Better Auth.

PlatonOP•4/17/25, 2:35 PM

Maybe mis-spoke, thought I saw in the docs somewhere that it would send an email notification upon changing user details

PlatonOP•4/17/25, 2:36 PM

Feel like a potential solution to this problem, which might open up more options, is letting us change default field options in addition to just changing the 'key', similair to what you can do to additionalFields (required, input)

PPlaton Maybe mis-spoke, thought I saw in the docs somewhere that it would send an email...

Ping•4/17/25, 2:36 PM

No, I don't believe we do this.
In any case, you can always fetch the user data based on email from your DB, then find their tenant id or whatever, and remove that from the prefix of the email to properly send emails, or do whatever you may want regarding email.

PlatonOP•4/17/25, 2:37 PM

Yeah can do

PlatonOP•4/17/25, 2:37 PM

Just seems hacky is all

PlatonOP•4/17/25, 2:37 PM

I can for sure use it

Ping•4/17/25, 2:38 PM

Yeah, I think this is best-case as far as I can tell.

PlatonOP•4/17/25, 2:38 PM

Just see this as a potential improvement

Ping•4/17/25, 2:38 PM

For BA so far, that is.

PlatonOP•4/17/25, 2:38 PM

Fair enough mate

PPlaton Just see this as a potential improvement

Ping•4/17/25, 2:40 PM

You're right. I'll add this to my to-do list and I'll think of solutions on having this built-in.
I'll ping you here if I have any news.

PlatonOP•4/17/25, 2:43 PM

Awesome thank you!

PPing No, I don't believe we do this. In any case, you can always fetch the user data ...

Ping•4/17/25, 2:46 PM

@Platon Just came up with a better idea for the email sending part.
Instead of querying your DB to remove the prefix, you could make each email's prefix use a dash or some special character before the real email, or any special character that couldn't be part of the email prefix.
So instead of querying your DB to find the id and remove said email prefix id, you can just replace everything in front of your special character/dash.

I hope i made sense

PlatonOP•4/17/25, 2:48 PM

Believe I get ya, still think the first solution works fine though

If I know im on tenant 1's site, and their tenant id is 123, if I just query for 123-{restofemail}, then thats my list of users

PlatonOP•4/17/25, 2:48 PM

Or maybe I misunderstood and your new solutions actually better?

PlatonOP•4/17/25, 2:50 PM

Either way actually, because I can't use the built in email system, I'll probably just have a separate column for both email and tenant, then the email column can just be some nonsense like uuid@email.com

PPlaton Either way actually, because I can't use the built in email system, I'll probabl...

Ping•4/17/25, 2:54 PM

Can I know why you can't use built-in method + the work-around with the prefixed email?
Just wondering since I want to have built-in support for your use-case and maybe this info is helpful

PlatonOP•4/17/25, 2:56 PM

DB searches are going to be slower, and I wouldn't be able to index properly against tenants/emails

PPlaton DB searches are going to be slower, and I wouldn't be able to index properly aga...

Ping•4/17/25, 3:00 PM

DB searches are going to be slower

With my new idea you won't need to do any additional DB queries.

Let me elaborate on my idea.
Say you have tenant ids, and say they are only just numbers.
When a new user signs up, the email will be

123-real@email.com

123-real@email.com

.
Then, say that same user works in a different org, when they sign-up again, it will say

321-real@gmail.com

321-real@gmail.com

.

Instead of querying your DB to find the tenant

id

id

and remove that from the prefix of the email, you can just use JS to remove everything in front of the

character.
Since you know that the tenant

id

id

is always numbers, and won't include

.
After removing everything in front of

in the email, it looks something like this:

123-real@email.com

123-real@email.com

real@email.com

real@email.com

PlatonOP•4/17/25, 3:01 PM

Yeah I totally get you, i just mean outside of registering, I still need to use the tenant id for certain actions, i.e. say I want to list all the accounts under a tenant

PlatonOP•4/17/25, 3:02 PM

So for that, I'd still have a separate column for tenant id

PlatonOP•4/17/25, 3:02 PM

Which is fine, its just duplication of data

Ping•4/17/25, 3:03 PM

Okay I understand you now. Thanks for your patience by the way :)

Ping•4/17/25, 3:03 PM

Okay yeah, in my idea for built-in support, we'd have a seperate field as well.

Anyway to allow shared emails?

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