Fillo

What is Fillo?

Fillo is a developer-focused, AI-friendly form infrastructure platform that lets teams build fully native forms directly inside their product without creating backend systems from scratch. Instead of using external form builders or iframes, it renders forms using your own UI components while handling everything behind the scenes—like schema, validation, file uploads, responses, and delivery workflows. It also supports coding agents, meaning you can describe a form in natural language and have it generated automatically, making it ideal for onboarding flows, support forms, and internal tools. Fillo acts as a “headless form backend,” letting developers focus on user experience while it manages the entire data and logic layer.

Engineered around the philosophy of “Never build another form by hand,” Fillo provides complete backend infrastructure so developers don't have to re-architect database schemas, file pipelines, or email triggers every time an application needs an onboarding flow, feedback widget, or support intake modal. Powered by @usefillo/react, Fillo lets AI coding agents (Claude Code, Cursor, Copilot, Windsurf) bootstrap and wire up production-ready forms from a single natural-language prompt. Supporting direct-to-S3/R2 multi-gigabyte file uploads (up to 5 GB), invisible user context attachment, and non-breaking schema versioning, Fillo provides a free forever tier of 200 responses/month alongside paid plans starting at €35 (~$39) per month.

• Developer / Company: Fillo (fillo.so)
• Core Architecture: Headless & Native React Form Engine, Direct Cloud Storage Uploader & CLI Agent Tooling
• Coding Agent Compatibility: Claude Code, Cursor, Windsurf, GitHub Copilot & MCP Clients via npx @usefillo/cli

Use Cases:

• Letting coding agents (Cursor, Claude Code) generate full-featured in-app feedback or support modals directly inside existing React/Next.js codebases
• Attaching hidden metadata (user ID, enterprise organization, current plan, active route, device info) to form submissions without prompting the user
• Allowing users to upload large files (up to 5 GB per file) directly from their browser straight to company-owned AWS S3, Cloudflare R2, Google Drive, or Box
• Building in-product approval votes, vendor review requests, feature priority rankers, and cancellation retention flows
• Modifying live production forms with schema versioning so new fields don't invalidate historical submission formats

Technology:

• Native @usefillo/react component library rendering standard accessible HTML controls styled directly by Tailwind, CSS Modules, or Vanilla CSS
• Browser-direct multipart upload pipeline streaming bytes securely into S3 or R2 buckets while preserving response associations
• Agent bootstrap protocol (npx @usefillo/cli@latest agent bootstrap) empowering agentic CLI tools to scaffold and connect forms autonomously

Target Users:

• Frontend and full-stack software engineers who want native in-product forms without building backend handling logic
• Developers building with AI coding agents (Claude Code, Cursor, Windsurf) looking to generate forms via prompt
• Product managers and growth leads needing customized user onboarding and cancellation review flows
• SaaS founders wanting client file uploads routed directly to private company cloud storage

Acquisition: Operates as an independent developer tools and form infrastructure platform (Fillo / fillo.so)

Key features of Fillo

Fillo's key platform features are

• Zero Iframes (100% Native DOM): Renders real HTML elements inside your route—allowing your existing design system, CSS variables, and fonts to style every input field.
• Coding Agent Bootstrap: Install the Build-with-Fillo skill; your coding agent (Claude Code, Cursor, Windsurf) inspects your codebase, asks what fields are needed, and writes working component code.
• Direct-to-Storage Cloud Uploads: Files bypass intermediary servers and upload browser-direct to your connected Amazon S3, Cloudflare R2, Google Drive, or Box storage (up to 5 GB resumable uploads).
• Invisible Context Attachment: Programmatically bind user email, account IDs, subscription tiers, current URL path, or application state to submissions without adding form fields.
• Non-Breaking Schema Versioning: Update active fields and validation rules in staging or production while preserving legacy data schemas on historical responses.
• Framework Versatility: Native components for React and Next.js, with headless hooks and lightweight adapters supporting Vue, Svelte, Astro, or plain JavaScript.
• Automated Downstream Webhooks: Route form submissions, context payloads, and durable file links into Slack, HubSpot, Zapier, or internal API webhooks in real time.
• Built-in Input Validation & Formatting: Out-of-the-box handling for email validation, phone number formatting with international country pickers, rating stars, and priority rankers.

Fillo Pricing

Fillo operates on a simple, response-volume pricing model with a permanent free tier and an all-inclusive pro plan, supported by a 30-day full-feature trial.

Free Forever Plan:

• €0 / Free Forever: 200 completed responses per month with no time limits and no credit card required
• Includes all rendering methods (React, hooks, headless), coding agent setup, custom CSS styling, and standard webhooks

Pro Plan:

• 30-Day Free Trial (access to all Pro capabilities)
• €35.00 (~$39.00) / month: 5,000 completed responses per month included
• Overages billed transparently at €0.007 (~$0.008) per additional response
• Direct cloud storage integrations (AWS S3, Cloudflare R2, Box, Google Drive), unlimited team seats, priority webhook delivery, and advanced schema versioning

Disclaimer: Completed responses are counted only when a user successfully submits a valid form. Unsubmitted drafts and abandoned views consume zero quota. For enterprise volume plans and custom security reviews, visit fillo.so/pricing.

Who is using Fillo?

Fillo is used by software engineers and modern product teams, including

• Full-Stack SaaS Builders: Embedding native bug reporting, customer feedback widgets, and feature request rankers directly into user dashboards
• Developers Using Coding Agents: Prompting Cursor or Claude Code to build complex intake flows without configuring databases or file handlers
• B2B Enterprise Platforms: Handling multi-gigabyte document intake and security questionnaires routed directly into corporate AWS S3 or Cloudflare R2 buckets
• Operations & Support Leads: Gathering customer support tickets with complete account and environment context attached automatically

Best Fillo Alternatives

Some of the strongest Fillo alternatives include

• Formspree (Form Backend API)
• Tally Forms (No-Code Form Builder)
• Typeform
• React Hook Form (Client-Side State Library)
• Baserow / Airtable Forms
• Jotform

Pros and Cons of Fillo

Pros

• Renders true native DOM elements inside your app rather than isolated, sluggish iframes
• First-class AI coding agent workflow (npx @usefillo/cli) allows Cursor and Claude Code to scaffold forms instantly
• Direct-to-storage uploads (S3, R2) support files up to 5 GB without burdening your web server
• Captures hidden application context (user identity, route, subscription tier) invisibly
• Generous free plan includes 200 responses per month with all render methods enabled

Cons

• Requires basic frontend development or coding agent familiarity (not a standalone no-code drag-and-drop page builder)
• Native component bindings currently center around React, requiring headless hooks for other frontend frameworks
• Advanced integrations like direct enterprise S3/R2 storage require upgrading to the €35/mo Pro tier

Why Choose Fillo?

Traditional form builders force you to embed foreign iframes that break your design consistency, create responsive layout headaches, and silo user data away from your product context. Building forms from scratch requires writing custom database models, file uploaders, and validation schemas. Fillo solves both sides of the equation.

• Keeps complete visual ownership of your user interface with native HTML elements and CSS
• Saves engineering hours by delegating form generation to your AI coding assistant
• Eliminates file upload server bottlenecks by streaming directly to your private S3 or R2 cloud storage
• Ensures submissions always include critical user and account context for immediate downstream action

Fillo vs. Competitors

The main difference between Fillo, Formspree, Typeform, and React Hook Form lies in the balance between UI integration and backend infrastructure. While React Hook Form handles only client-side state without backend storage, and Typeform relies on embedded iframes, Fillo provides both native React UI components and fully managed backend infrastructure—complete with direct-to-S3 uploads, hidden context capture, and AI agent bootstrap commands.

How do we rate Fillo?

Fillo Review

Fillo delivers a long-overdue modernization of web form architecture. By eliminating the compromises of third-party iframes while simultaneously removing the burden of writing backend database routes and file handlers, Fillo hits the exact sweet spot for modern web development. Its seamless integration with AI coding agents like Cursor and Claude Code enables developers to go from conversational prompts to working in-app forms in seconds. With direct-to-cloud file streaming, schema versioning, and hidden context capture, Fillo sets a new benchmark for developer-first form infrastructure.

Conclusion

Fillo is a modern headless form infrastructure platform that lets developers build fully native forms directly inside their apps without having to create backend systems from scratch. Instead of using iframes or third-party embeds, it renders forms using your own components and design system while handling everything behind the scenes—schema management, validation, file uploads, responses, and delivery pipelines. Its biggest strength lies in this separation of concerns: your product keeps full control over UI, routing, and context, while Fillo manages the complex logic and data layer, including integrations with tools like Slack, webhooks, and storage services. Built for use cases like onboarding, support, feedback, and approvals, it eliminates the need to rebuild form infrastructure repeatedly across projects. While it’s still in early access and may require some setup, the value is clear.