I'm building a web app and need a database that plays well with ORMs

If your top priority is ORM compatibility, the safest default choice is usually PostgreSQL.

Why PostgreSQL works well with ORMs

• Very widely supported by popular ORMs: Prisma, Django ORM, SQLAlchemy, Sequelize, TypeORM, Hibernate, Entity Framework, etc.
• Rich relational features that ORMs can map cleanly:
  • foreign keys
  • transactions
  • joins
  • constraints
  • enums
  • JSON columns when you need flexibility
• Reliable and mature, so less likely to surprise you later as the app grows.

Good alternatives

• MySQL / MariaDB
  Also widely supported and fine for many apps, though PostgreSQL is often preferred for more advanced querying and data integrity.
• SQLite
  Great for prototyping, local dev, and small apps. Many ORMs support it well, but it’s usually not the best long-term choice for concurrent production workloads.
• SQL Server
  Strong ORM support, especially if you’re in the Microsoft ecosystem.

Recommendation

• Start with PostgreSQL if you want the most flexible, ORM-friendly production database.
• Use SQLite for early development/testing if simplicity matters.
• Choose MySQL if your stack or hosting environment already favors it.

If you want, I can also recommend a database based on your specific ORM or stack, like Prisma + Next.js, Django, or Rails.