SignatureAPI review (2026): is it worth $25 a month?
E-signature API for developers, with a no-code connector
Black Friday: is there a SignatureAPI sale?
SignatureAPI report card
Fair · out of 4.0 · graded Nov 13, 2026
Best for adding e-signatures to your own app
SignatureAPI is an e-signature API for developers: Standard is $25 a month with 100 envelopes, then $0.25 each. The free test account has no time limit, and only completed envelopes are billed. Its signatures are eIDAS simple signatures, not advanced or qualified ones, so you write code to use it.
Who SignatureAPI is for
- Fits if you are building signing into your own product
- Works for developers who want to pay per completed envelope
Who SignatureAPI is not for
- Not for you if you have no developer, since it is an API with only connectors for no-code
- Watch out: the signatures are eIDAS simple only, not advanced or qualified
- Tight if your envelopes are large, as the limit is 10 documents and 10 signers
- Watch out: annual billing and prepaid credits are not self-serve
Why SignatureAPI gets a 2.0
Five grades, each with its reason. The GPA is their average: an A is 4 points, an F is none.
- CValue for moneyStandard is $25 a month with 100 envelopes included, then $0.25 each, just above the category's $20 middle. Extra dashboard users are $20 each.
- CFree plan and trialA free test account with no time limit and no card, but it is for testing, and sending for real needs Standard.
- CFeaturesEnvelope API, templates, signing with no account, sealed documents, audit log, branding and webhooks. An envelope holds at most 10 documents and 10 signers, and signatures are simple only.
- DEase of useNo store rating on record, and it needs developers to write code against an API before anyone signs anything.
- BPlatforms and integrationsWeb and API, with Power Automate and Zapier connectors.
What these grades rest on. Graded from this listing, whose facts were read from SignatureAPI's own pages on 13 November 2026. Not based on using the product, and shorter than our full reviews. How we review and grade.
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<a href="https://toolgpa.com/tools/signatureapi#review"><img src="https://toolgpa.com/badge/signatureapi.svg" alt="SignatureAPI: 2.0 GPA on ToolGPA" width="196" height="56"></a>Where SignatureAPI stands among e-signature and proposal tools
SignatureAPI's GPA of 2.0 is higher than 19 of the 78 other e-signature and proposal tools we grade, and level with 18.
It stands best on platforms and integrations (B, above 12 of 78) and worst on ease of use (D, above 1).
Its paid plans start at $25 a month, against a middle price of $19 for the category: 34 of the 54 others that charge start lower.
On features, ease of use and platforms it scores 2.0 out of 4. 29 tools score higher and cost less.
Each grade against the category
Every bar is all 79 e-signature and proposal tools we grade, cut by the letter each got. SignatureAPI’s own letter is outlined.
- CValue for moneyAbove 14 of 78, level with 52
- CFree plan and trialAbove 32 of 78, level with 40
- CFeaturesAbove 1 of 78, level with 55
- DEase of useAbove 1 of 78, level with 1
- BPlatforms and integrationsAbove 12 of 78, level with 65
Price against what you get
Each dot is one of 55 e-signature and proposal tools. Further left costs less, and higher up scores better on features, ease of use and platforms. Point at a dot to see which tool it is.
Features, ease of use and platforms, averaged
What paid plans start at, a month (each step along is roughly double) →
- The best score at each price
- Has a free plan
- No free plan
Keep SignatureAPI, or make your own?
Keep it
To replace SignatureAPI you would be making connections to other products, each kept working as those products change. That is not a weekend's work, with an AI app builder or without one.
That makes this kind of software worth paying for, not this one in particular: 41 of the 78 other e-signature and proposal tools grade higher. It costs $300 a year.
What you could make
- Templates: an app builder makes this well.
What you could not
- Connections to other products, each kept working as those products change.
- An AI agent, with the models and the safeguards behind it.
- What a company asks for before it lets staff use something: audit logs.
What this rests on. SignatureAPI’s listing: what it does, where it runs, what it plugs into and what it costs. It is a judgement about the kind of software this is. We have not built a replacement for it, and making your own means looking after it too. How we decide, and every tool’s verdict.
What is SignatureAPI?
SignatureAPI is an electronic signature service built to be called from other software. Developers create an envelope over a REST API, generate documents from .docx templates and receive the signed file with an audit log. Connectors for Power Automate and Zapier and an AI toolkit cover people who do not write code.
Worth knowing
- Only completed envelopes, signed by every recipient, are billed; the $0.25 rate applies after the first 100 each month.
- An envelope holds at most 10 documents and 10 signers.
- The vendor classifies its signatures as eIDAS simple electronic signatures (SES), not advanced or qualified ones.
- Annual billing and prepaid credits are not self-serve; the vendor says to contact it.
Key features
- Envelope API
- One call creates an envelope with up to 10 documents and up to 10 signers, routed in parallel or in sequence.
- Document templates
- Start from a .docx file with placeholders and fill it with data from your own system before the document goes out for signature.
- Accountless signing
- Signers open a link and sign from a desktop or phone browser without creating an account.
- Sealed documents and audit log
- The finished file holds the signed documents and a log of who opened it and what they did, cryptographically sealed against changes.
- Branding and languages
- Logo and brand colors can be applied to the signing page and recipient emails, and the interface language, date format and time zone can be set.
- Webhooks and no-code connectors
- Webhooks and emails report signing activity in real time. Power Automate and Zapier connectors and an AI toolkit are offered for non-developers and agents.
SignatureAPI pricing
As of Nov 13, 2026, SignatureAPI is a paid product with a free trial, starting at $25 per month, includes 100 completed envelopes.
- Starts at
- $25 per month, includes 100 completed envelopes
- Free plan
- None
- Free trial
- Free test account with no time limit, no card required
| Plan | Price | What you get |
|---|---|---|
| Standard | $25per month, includes 100 envelopes | First 100 envelopes included, then $0.25 each. One dashboard user included, extra users $20 each. |
| Enterprise | Custom | Annual contracts, prepaid credits, SLAs and dedicated Slack support, sold through sales. |
Read from signatureapi.com on Nov 13, 2026. Prices change, so confirm with SignatureAPI before you buy.
Works with
SignatureAPI alternatives
- SignatureAPI vs Anvil
Free plan · from $99/mo
- SignatureAPI vs Firma
Free trial · from €0.049
- SignatureAPI vs eSignatures.io
Free trial · from $0.49
- SignatureAPI vs BoldSign
Free plan · from $5/mo
- SignatureAPI vs Dropbox Sign
Free plan · from $15/mo
Common questions
Does SignatureAPI have an Android app?
No Android app was listed when its pages were read on Nov 13, 2026. SignatureAPI is listed for Web.
Does SignatureAPI have an iPhone app?
No iPhone app was listed when its pages were read on Nov 13, 2026. SignatureAPI is listed for Web.
Is SignatureAPI open source?
SignatureAPI is not described as open source on its own site, as read on Nov 13, 2026.
Does SignatureAPI have an API?
Yes. SignatureAPI offers a public API, according to its own site.
Sources for this page
The prices, plans, platforms and features above were read from these pages on Nov 13, 2026.