Formstack
Formstack is a no-code workplace productivity platform spanning online forms, document generation, electronic signature, and workflow automation. The developer portal at developers.formstack.com exposes a REST API (v2025.0) for forms, submissions, fields, webhooks, folders, and partial submissions, plus product-specific surfaces for Formstack Documents, Formstack Sign, and Formstack Workflows. Authentication uses OAuth 2.0. Machine-readable indexes and OpenAPI artifacts are surfaced at developers.formstack.com/llms.txt.
Formstack publishes 9 APIs on the APIs.io network. Tagged areas include Forms, Documents, eSignature, Workflow Automation, and No-Code.
Formstack’s developer surface includes documentation, changelog, GitHub presence, and 4 more developer resources.
APIs
Formstack Forms API
REST API for creating, reading, updating, and deleting forms in a Formstack account, including form configuration, styling, and access rules.
Formstack Submissions API
Read, create, update, and delete form submissions; supports filtering by date, search, and field values. Returns submitted field data and metadata.
Formstack Fields API
Programmatically manage form fields - text, select, file upload, signature, payment, calculation, and others - including ordering, validation, and conditional logic.
Formstack Webhooks API
Configure webhook subscriptions to receive submission events at a customer-provided URL, with retry semantics for failed deliveries.
Formstack Folders API
Manage folder organization for forms within a Formstack account.
Formstack Documents API
Programmatic interface to Formstack Documents (formerly WebMerge) for generating PDFs, Word docs, and other templated documents from data payloads.
Formstack Sign API
Electronic signature API for sending documents for signature, tracking status, and retrieving signed copies. Part of the Formstack Suite.
Formstack Workflows API
Workflow automation surface for routing submissions, documents, and approvals across multi-step business processes.
Formstack OAuth 2.0
OAuth 2.0 authorization server used to authenticate API clients and issue access tokens for the Formstack REST API.