Penpact vs OpenSign: an open-source e-signature comparison
OpenSign and Penpact are both open-source, self-hostable e-signature tools, but they solve different problems. OpenSign is a complete signing application you host and your team logs into, with its own dashboard, templates, and signer management. Penpact is an e-signature engine you embed in your own product through a typed API and SDK, so your users sign without ever leaving your app. If you want a ready-made signing portal for your company, OpenSign fits. If you are a developer building signing into software you ship, Penpact is built for that. The detail is below.
Penpact vs OpenSign at a glance
| Penpact | OpenSign | |
|---|---|---|
| What it is | embeddable e-signature API + SDK | standalone signing app |
| Open source | Yes (AGPL-3.0) | Yes (AGPL-3.0) |
| Self-host | Yes (docker compose up) | Yes |
| Primary interface | typed TypeScript SDK + REST | web dashboard |
| Embedding in your product | first-class (native-feeling) | iframe / link-based |
| AI field detection | included (Claude, Gemini, or GPT) | not built in |
| White-label / branding | free in the open core | available |
| Audit trail + certificate | yes | yes |
| Maturity | early (v0.1.0, June 2026) | more established |
Details reflect each project’s public positioning in 2026. Confirm the current state of each before you decide.
What is the difference between Penpact and OpenSign?
The difference is embed versus host-and-use. OpenSign gives you a full product: you deploy it, create accounts, and your team prepares and sends documents from its dashboard. Penpact gives you the signing engine as an API: you call it from your own backend, place fields by coordinate or let AI propose them, and drop a signing experience straight into your interface. OpenSign is the destination; Penpact is the building block. Teams that just need an internal tool tend to prefer OpenSign. Product teams that need signing to feel like a native feature tend to prefer Penpact.
Which is better for embedding e-signatures into an app?
Penpact is designed for embedding from the first line of code. It ships a small, hand-written TypeScript SDK and an embeddable signing flow that you theme to match your product, so signers see your brand rather than a third-party portal. OpenSign can be linked to or framed, but it was built as an app first, so deep, native integration takes more work. If “signers never leave our product” is a requirement, that is the clearest reason to choose Penpact. See the Next.js guide or the React guide for what the integration actually looks like.
Are OpenSign and Penpact both free and open source?
Yes. Both are licensed under AGPL-3.0, so you can read the source, self-host, and modify them, as long as you honor the copyleft terms. With Penpact, docker compose up starts Postgres and the API and prints a working key, and the managed cloud is the paid tier for teams that would rather not run infrastructure. The practical question is rarely “is it free” but “which model fits my product”: a hosted app you operate (OpenSign) or an engine you embed and bill on usage (Penpact).
Does OpenSign have AI field detection?
OpenSign does not include AI field placement; you position signature, name, and date fields yourself. Penpact can point a vision model at the PDF and propose those fields for you, then let you adjust them in a drag-and-drop builder. It supports Claude, Gemini, or GPT, and self-hosting requires your own provider key. When no key is set, the endpoint simply returns no proposals instead of failing, so the rest of the flow keeps working. For documents with many signature blocks, this removes most of the tedious coordinate work.
When should you choose OpenSign, and when Penpact?
Choose OpenSign if you want a finished, self-hostable signing application for your team to log into and operate today, and you do not need to embed it deeply into another product. Choose Penpact if you are a developer adding signing to software you build, you want a typed SDK and AI field detection, and usage-based pricing with no per-seat fees matters to you. Penpact is honest about being early (v0.1.0): the tradeoff is maturity for a developer-first, embeddable design.