The SignatureAPI Insider’s Guide
Everything we know about SignatureAPI in one document: what it costs, its grades, getting a refund, getting help and what else to look at. Read it here, or keep a copy.
SignatureAPI
The Insider’s Guide
E-signature API for developers, with a no-code connector
Every plan, grade, refund rule and rival among e-signature and proposal tools, read from SignatureAPI’s own pages.
Made by Signature API, Inc. · checked Nov 13, 2026 · toolgpa.com
Contents
- 01WelcomeWhat it is, who it suits, its grades and the ten things to know first
- 02What it costsEvery plan, the free plan, ways to pay less and how prices have moved
- 03What it doesIts main features, where it runs, what it works with and who makes it
- 04Where it standsIts grades against its category, and whether to keep it or make your own
- 05The alternativesThe tools it is most often weighed against, side by side
- 06Quick answersThe questions people ask about it, each answered in a line or two
- 07About ToolGPAWho made this guide, what else is on the site, and how to cite it
ToolGPA put this guide together from SignatureAPI’s own pages, its app-store listings and our grades. Every fact in it is on SignatureAPI’s page too, where it is kept up to date. Checked Nov 13, 2026.
Part 01 · Overview
Welcome
What it is, who it suits, its grades and the ten things to know first
2.0
GPA, above 19 of the 78 other e-signature and proposal tools we grade
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.
To get you started, here are 9 things to know about SignatureAPI, taken from its own pages and our grades.
Its signatures are eIDAS simple signatures, not advanced or qualified ones, so you write code to use it.
- 1
Best for adding e-signatures to your own app
The free test account has no time limit, and only completed envelopes are billed.
- 2
Paid plans start at $25 a month
As its pricing page puts it: $25 per month, includes 100 completed envelopes.
- 3
You can try it first
Free test account with no time limit, no card required
- 4
It runs on Web
Web.
- 5
Envelope API
One call creates an envelope with up to 10 documents and up to 10 signers, routed in parallel or in sequence.
- 6
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.
- 7
Accountless signing
Signers open a link and sign from a desktop or phone browser without creating an account.
- 8
A 2.0 GPA, above 19 of 78
That is against the other e-signature and proposal tools we grade, on value, the free plan, features, ease of use and platforms.
- 9
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.
SignatureAPI at a glance
- Pricing
- Free trial, from $25 per month, includes 100 completed envelopes
- Free plan
- No
- Free trial
- Free test account with no time limit, no card required
- Runs on
- Web
- Made by
- Signature API, Inc.
- Category
- E-Signatures & Proposals
- Our grade
- 2.0 GPA, fair
The report card
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.
| Subject | Grade | Comment |
|---|---|---|
| Value for money | C | Standard 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. |
| Free plan and trial | C | A free test account with no time limit and no card, but it is for testing, and sending for real needs Standard. |
| Features | C | Envelope 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. |
| Ease of use | D | No store rating on record, and it needs developers to write code against an API before anyone signs anything. |
| Platforms and integrations | B | Web and API, with Power Automate and Zapier connectors. |
An A is worth 4 points, a B 3, a C 2, a D 1 and an F nothing. The GPA is the average of the five.
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 it 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
Good to know
Good for
- Developers adding signing to a SaaS product
- Teams sending a few hundred envelopes a month on a flat per-envelope rate
- Low-code teams automating signature requests with Power Automate or Zapier
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.
Part 02 · Pricing
What it costs
Every plan, the free plan, ways to pay less and how prices have moved
$25
A month to start
SignatureAPI is a paid product with a free trial, starting at $25 per month, includes 100 completed envelopes.
A free test account with no time limit and no card, but it is for testing, and sending for real needs Standard.
Standard
$25
per 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.
Trying it first
Free test account with no time limit, no card required
Read from signatureapi.com on Nov 13, 2026.
Part 03 · Features
What it does
Its main features, where it runs, what it works with and who makes it
1
Place it runs: Web
E-signature API for developers, with a no-code connector. Here is what it does, as its own site describes it, and what it covers: public API, templates, workflow automation, AI agents.
Envelope API, templates, signing with no account, sealed documents, audit log, branding and webhooks.
- 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.
Where it runs
- Web
What it works with
- Power Automate
- Zapier
SignatureAPI is made by Signature API, Inc.
Part 04 · Standing
Where it stands
Its grades against its category, and whether to keep it or make your own
19/78
Other e-signature and proposal tools it is graded above
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
- CFree plan and trialAbove 32 of 78
- CFeaturesAbove 1 of 78
- DEase of useAbove 1 of 78
- BPlatforms and integrationsAbove 12 of 78
Price against what you get
Each dot is one of 55 e-signature and proposal tools. Further left costs less; higher up scores better on features, ease of use and platforms. SignatureAPI is the marked dot.
What paid plans start at, a month (each step along is roughly double) →
Keep it, or make your own?
Whether this is something you could build for yourself with an AI app builder, and what you would give up.
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.
Part 05 · Alternatives
The alternatives
The tools it is most often weighed against, side by side
Anvil, Firma, eSignatures.io, BoldSign and Dropbox Sign
The 5 tools SignatureAPI is most often weighed against, with where each one differs from it.
- 2.2GPA
Anvil
Free plan · from $99/mo
Document automation and e-signature APIs for developers.
- Anvil has a free plan. SignatureAPI does not, though it has a free trial.
- SignatureAPI also covers AI agents.
- Anvil also covers forms.
- 2.4GPA
Firma
Free trial · from €0.049
- 2.0GPA
eSignatures.io
Free trial · from $0.49
Pay-per-contract e-signatures with an API and no monthly fee.
- SignatureAPI also covers AI agents.
- eSignatures.io also covers documents.
- 3.0GPA
BoldSign
Free plan · from $5/mo
Low-cost e-signature app and API from Syncfusion.
- BoldSign has a free plan. SignatureAPI does not, though it has a free trial.
- Only BoldSign lists iOS and Android apps.
- SignatureAPI also covers workflow automation and AI agents.
- 2.0GPA
Dropbox Sign
Free plan · from $15/mo
E-signature app from Dropbox with unlimited requests on paid plans.
- Dropbox Sign has a free plan. SignatureAPI does not, though it has a free trial.
- SignatureAPI also covers workflow automation and AI agents.
- Dropbox Sign also covers documents.
Part 06 · Questions
Quick answers
The questions people ask about it, each answered in a line or two
13
Questions, each answered in a line or two
The short version of everything above, for when you only need the answer. Each one is told in full in its part of the guide.
Is SignatureAPI free?
No, SignatureAPI is a paid product, but you can try it first. Free test account with no time limit, no card required.
How much does SignatureAPI cost?
SignatureAPI lists 2 plans. Standard: $25 per month, includes 100 envelopes.
What platforms does SignatureAPI work on?
SignatureAPI is available on Web.
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.
What does SignatureAPI integrate with?
SignatureAPI's listing names Power Automate and Zapier. A listing names up to eight integrations, so it may connect to more.
Who makes SignatureAPI?
SignatureAPI is made by Signature API, Inc.
What are the alternatives to SignatureAPI?
The closest alternatives to SignatureAPI in our directory are Anvil, Firma, eSignatures.io, BoldSign and Dropbox Sign.
How does SignatureAPI compare with other 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.
Is SignatureAPI good value for money?
ToolGPA grades SignatureAPI C for value for money. 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.
Could I make my own version of SignatureAPI?
To replace SignatureAPI you would be making connections to other products, each kept working as those products change.
Where this guide comes from
The prices, plans, platforms and features were read from SignatureAPI’s own pages on Nov 13, 2026, and the grades were given on Nov 13, 2026. 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.
Every tool we list gets five grades, A to F, each with its reason, and a GPA that averages them. How each is decided is at toolgpa.com/grades. This guide is ToolGPA’s own work; it is not made, paid for or approved by Signature API, Inc. Prices change, so check signatureapi.com before you buy.
Part 07 · About
About ToolGPA
Who made this guide, what else is on the site, and how to cite it
7,721
Tools graded, in 95 categories
ToolGPA grades software the way a school report grades a pupil: five subjects, a letter for each with the reason written beside it, and a GPA that averages them. Prices, plans and platforms are read from each maker’s own pages and dated, so you always know how fresh a figure is.
Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Every tool on the site has a guide like this one, free to download and pass on. It all lives at toolgpa.com.
7,721
tools graded
95
categories
739
price changes on record
579
apps priced in 12 countries
What else is on toolgpa.com
- SignatureAPI, kept up to dateEverything in this guide, with prices and grades as they are todaytoolgpa.com/tools/signatureapi
- How grades are givenThe rules behind every letter and every GPAtoolgpa.com/grades
- Value chartsWhat each tool costs against what it scores, for every categorytoolgpa.com/charts
- CompareAny two tools side by side, plan by plantoolgpa.com/compare
- Price changesEvery price rise and cut on record, each with its sourcetoolgpa.com/price-changes
- Prices by countryWhat apps cost on the App Store in 12 countriestoolgpa.com/prices-by-country
- Pay lessEvery public discount: yearly billing, students, nonprofitstoolgpa.com/save
- Keep or makeWhich tools are worth paying for, and which you could build yourselftoolgpa.com/keep-or-make
Scan for the live page
Prices and grades as they are today
Quoting this guide?
Please name ToolGPA and link to the live page, so readers can check the figures for themselves:
ToolGPA, "SignatureAPI: The Insider's Guide", checked Nov 13, 2026. https://toolgpa.com/tools/signatureapi
Know someone choosing between e-signature and proposal tools?
Send them this guide: toolgpa.com/tools/signatureapi/guide
ToolGPA elsewhere: youtube.com/@toolgpa
See our other guides
The best-graded e-signature and proposal tools after SignatureAPI, each with an Insider's Guide of its own.
- E-Signatures & Proposals Insider's GuideEvery one of the 79 e-signature and proposal tools we grade, compared
- BoldSign Insider's GuideLow-cost e-signature app and API from Syncfusion3.0 GPA
- Zoho Sign Insider's GuidePer-user e-signature app from Zoho with a free single-user plan3.0 GPA
- Docusign Insider's GuideE-signature service for sending, signing and tracking agreements2.6 GPA
Choosing software? Every tool graded, every price dated.
Compare tools at toolgpa.com ›Everything in this guide is ToolGPA’s own summary of what SignatureAPI’s pages, its app-store listings and public reviews said on the dates shown. Grades are our judgement under the rules at toolgpa.com/grades. Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. SignatureAPI is a trademark of its owner, and this guide is not made, paid for or approved by Signature API, Inc. Prices and plans change: check signatureapi.com before you buy.