The US government tried really hard to screw up email
We've published a new blog post: > While other projects floundered in red tape, email thrived in it. Read it here!
Public postmortem: database connection exhaustion
We've published a new blog post: > Our public postmortem for the incident on March 31st, 2026. Read it here!
Updates from March
Everything you ever wanted to know about our API versioning We’re extremely proud of our API, especially how we handle versioning. No matter how many updates...
Ask a nerd: what is the best way to unsubscribe from newsletters?
We've published a new blog post: > The email feature that got added because people kept marking email newsletters as junk. Read it here!
Bookshop.org embeds
We've published a new blog post: > Share book recommendations with rich embeds from Bookshop.org Read it here!
Email was into agents before they were cool
We've published a new blog post: > It turns out you’ve been using agents since way before the AI variety started deleting everything in their owners’...
Passwordless login
We've published a new blog post: > Skip the password entirely and sign in with just your passkey. Read it here!
Rename metadata keys in bulk
We've published a new blog post: > "First name" and "first_name", together at last Read it here!
A spring cleaning for our legal docs
We've published a new blog post: > Updated DPA, privacy policy, sub-processor list, and cookie policy. Read it here!
Ask a nerd: what happens when you click the spam button?
We've published a new blog post: > Honestly, it’s more conceptually complicated than technically complex. Read it here!
Safer defaults for the email creation API
We've published a new blog post: > A new API version that defaults to draft instead of sending, with a one-time confirmation header for immediate sends. Read...
Passkey support for two-factor authentication
We've published a new blog post: > Use your fingerprint, face, or security key as a second factor when signing in. Read it here!
How Buttondown's API versioning works
We've published a new blog post: > A deep dive into our date-based API versioning system, inspired by Stripe, and how it lets us ship breaking changes...
How we enabled Content Security Policy for everyone
We've published a new blog post: > Invisibly making your newsletter safer Read it here!
New API changes for Buttondown
Every ID in Buttondown's API is a UUID (e.g., ) with no indication of what it represents. UUIDs are great for databases, but they're not human-friendly....
How we migrated to TypeIDs without breaking clients
We've published a new blog post: > Making every ID in our API self-describing, one endpoint at a time Read it here!
How to send email to space
We've published a new blog post: > The first email was sent from space three days after the first webpage was published. Read it here!
Recovery codes for two-factor authentication
We've published a new blog post: > If you lose your authenticator device, recovery codes let you get back into your account. Read it here!
Filter sent emails by engagement rate
We've published a new blog post: > Quickly find your best (and worst) performing emails by filtering on open rate, click rate, and delivery rate. Read it here!
Updates from February
Custom templates for all You can write a Buttondown email template from scratch You’re not writing a Buttondown. You’re writing your newsletter. It should be...
