head to head · open source
Polar vs SolidInvoice
Polar has 10,270 GitHub stars, 787 forks, 141 open issues and last shipped yesterday. SolidInvoice has 971 stars, 235 forks, 190 open issues and last shipped 2 days ago. Polar leads on adoption by 958% (10,270 vs 971 stars). Polar is written in Python under Apache-2.0; SolidInvoice is written in PHP under MIT. Polar has attracted 8% as many forks as stars, SolidInvoice 24%. Polar was the more recently maintained of the two, and both are self-hostable with no licence fee.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| Polar | SolidInvoice | |
|---|---|---|
| GitHub stars | ★ 10K | ★ 971 |
| License | Apache-2.0 | MIT |
| Written in | Python | PHP |
| Last push | 2026-09-17 | 2026-09-16 |
| Forks | ⑂ 787 | ⑂ 235 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick Polar if
- You weight community size — 10K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick SolidInvoice if
- You want the SolidInvoice feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches PHP
- You evaluated both and SolidInvoice fits your workflow better
About Polar
Polar is an open source billing platform and payment infrastructure project for digital products, SaaS applications, and AI workloads. It is written in Python, licensed under Apache 2.0, and built around FastAPI, Next.js, React, and Turborepo. The project positions itself as a financial layer for software that needs to charge for tokens, agents, compute, subscriptions, and usage based models.
read the full Polar overview →
About SolidInvoice
SolidInvoice is an MIT licensed, self hostable invoicing and billing platform built on Symfony and PHP for freelancers and small businesses that want to send quotes and invoices without handing their client data to a subscription SaaS.
read the full SolidInvoice overview →
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Frequently asked questions
Is Polar or SolidInvoice more popular?
Polar has 10,270 GitHub stars and SolidInvoice has 971. Polar has the larger community by that measure.
Are Polar and SolidInvoice free?
Both are open source. Polar is licensed under Apache-2.0 and SolidInvoice under MIT. Neither carries a licence fee.
What is the difference between Polar and SolidInvoice?
Polar is written in Python and SolidInvoice in PHP. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, Polar or SolidInvoice?
Choose Polar if you want the larger community (10,270 stars) or its Apache-2.0 licence terms. Choose SolidInvoice if its feature set, stack or MIT licence fits better. Both are self-hostable.