OpenSign

OpenSign is an open-source PDF e-signature product for individuals and organizations that need document signing, reusable templates, or developer-led workflows. It is a strong fit when self-hosting or API integration matters; the free plan’s invitation-email cap and paid gates on key API functions are important constraints.

Overview

OpenSign brings document preparation, signing, storage, and security into one workflow. Its free plan pairs unlimited digital signatures and templates with completion certificates, sequential signing, OpenSign Drive, and email notifications. That is a generous starting point for occasional use, but unlimited signatures do not mean unlimited sending: the free plan allows up to 15 invitation emails per month.

Security features include TLS-encrypted transport, audit trails, IP logging, and tamper-evident signed PDFs. Two-factor authentication and passkey sign-in add account protection. These controls suit users who need a traceable signing process, though they do not change the limits on free-plan sending or production API access.

Key features

Templates and workflows

Reusable templates can include pre-placed widgets, reducing repeated document setup. The API supports self-signing, drafts, signer roles, and real-time webhook notifications, giving developers tools to connect signing steps with a wider process. Templates can be embedded in React, Next.js, HTML, JavaScript, and Angular projects. That makes OpenSign more compelling for product teams than for someone who only needs an occasional standalone signature.

Bulk sending and public template links require a paid plan. These restrictions matter for teams distributing the same document at scale or inviting signers through a public link: the free plan’s unlimited signature allowance will not cover those workflows.

Sending and account security

Users can configure SMTP through Gmail or other providers, although some SMTP features are reserved for paid plans. SMS authentication is supported, and signing can be sequential or use another supported signing order. Together with audit trails and IP logging, these options give organizations meaningful control over document handling without making every security feature a paid-plan differentiator.

Self-hosting

OpenSign provides Docker self-hosting instructions for Linux, macOS, and Windows. This is a practical advantage for organizations that want to run the software in their own environment. The trade-off is that self-hosting calls for an organization willing to manage deployment rather than relying only on a hosted service.

Pricing

OpenSign uses a freemium model. Its Free plan costs nothing and includes unlimited digital signatures and templates, completion certificates, sequential signing, OpenSign Drive, and email notifications. The 15-invitation-email monthly cap is the key operational limit; bulk sending and public links are paid-plan features. Sandbox API tokens are available on every plan, but live API tokens require Professional or Teams.

Professional has custom pricing and includes 240 API signatures per year, up to 10 signers per document, and up to 240 bulk documents. It is aimed at organizations whose API and bulk volumes fit those allowances. Teams also has custom pricing, with 500 API signatures per year, up to 10 signers per document, and up to 500 bulk documents; its larger quotas suit teams with heavier throughput. Both plans preserve the 10-signer ceiling, so they are not a fit for documents needing more signers.

Enterprise has custom pricing and adds a custom domain, whitelabeling, an uptime SLA, SSO support, and priority support. It is the relevant tier for organizations that need branded deployment or contractual service commitments. The free tier is the only plan with a stated price, so buyers should weigh the paid plans by their quotas and required features rather than assume a particular upgrade cost.

Platforms

OpenSign supports web, API, Linux, macOS, Windows, and self-hosted use. The breadth is useful for both browser-based signing and organizations deploying their own instance; Docker instructions cover the three desktop operating systems.

Who it's for

OpenSign suits individuals and businesses, from startups to large corporations, especially when reusable templates, embedded signing, self-hosting, or API-driven workflows are priorities. The free plan works for lower-volume signing that stays within 15 invitation emails per month. Teams that need bulk delivery, public links, or live API tokens should plan for a paid tier; organizations needing extensive service commitments or branding should consider Enterprise.

Pros and cons

• Pro: Unlimited signatures and templates on the free plan make it viable for users whose invitation-email volume remains low.
• Pro: Audit trails, IP logging, tamper-evident PDFs, two-factor authentication, and passkey sign-in cover document and account security needs.
• Pro: API workflows, web-framework embedding, and Docker self-hosting give developers and organizations several deployment paths.
• Con: The free plan stops at 15 invitation emails a month and excludes bulk sending and public links, limiting routine distribution.
• Con: Live API tokens require Professional or Teams, and both paid plans have custom pricing rather than a stated amount.
• Con: Professional and Teams cap documents at 10 signers, which may rule them out for larger signing groups.

Alternatives

Digital Signature API Software is a useful category to compare if API-first signature tools are the priority. For a broader view of signing products, browse E-Signature Software or Electronic Signature Software.

• PandaDoc is a freemium alternative with a free plan and web, mobile, and API platforms; choose it if those platforms or its yearly 60-document allowance suit your needs better.
• Dropbox Sign API offers a free package capped at three signature requests per month and a separate test mode; consider it if a smaller request allowance and API testing are a better fit.
• Signater has a free plan limited to three envelopes per month, one user, and three signers per envelope; it may suit a user whose modest envelope volume fits those bounds.
• Skribble offers a free Starter plan with pay-per-signature SES, AES, and QES pricing; consider it if those per-signature options are a better match.
• Xodo Sign has a free API sandbox, one document per week, one signer, and one seat; it is an option for especially light usage.
• BoldSign offers a free Essential plan with 25 envelopes per month and two templates; choose it if those envelope and template allowances better match your workload.
• PearSign has a free plan capped at three envelopes per month, three templates, and one user; it may work for an individual with low monthly volume.
• Documenso is another option if you want an open-source product with API and self-hosted platforms.

Verdict

OpenSign is best for individuals and organizations that value reusable templates, developer integration, or self-hosting and can work within its sending limits or budget for a paid tier. Its unlimited free signatures and strong workflow and security provisions are persuasive; look elsewhere if you need unrestricted free sending, live API tokens at no cost, or more than 10 signers per document on the listed paid tiers.