---
title: "PDF form data formats | Nutrient"
canonical_url: "https://www.nutrient.io/guides/web/forms/introduction-to-forms/data-formats/"
md_url: "https://www.nutrient.io/guides/web/forms/introduction-to-forms/data-formats.md"
last_updated: "2026-05-30T02:20:01.397Z"
description: "Use this guide to choose form data formats for browser form authoring workflows, including when to use Instant JSON, XFDF, or server-backed Document Engine storage."
---

# PDF form elements and data formats

Under the hood, PDF form elements are a type of PDF annotation called “widget” annotations. They’re used to implement interactive form elements, such as buttons, checkboxes, combo boxes, and more.

Widgets that can hold a value — like checkboxes, combo boxes, and text fields — store their data separately in an entity called a form field. All data formats Nutrient supports for encoding annotations are designed to also encode the values of form fields. Refer to the [annotation data formats](https://www.nutrient.io/guides/web/annotations/introduction-to-annotations/data-formats.md) guide to learn more.

## When to use each format

Use this table to choose the form data format based on your workflow requirements.

| Format                                                           | Use when                                                                          |
| ---------------------------------------------------------------- | --------------------------------------------------------------------------------- |
| [Instant JSON](https://www.nutrient.io/guides/web/forms/fill-form-fields/import-from-instant-json.md)                         | You need the default internal persistence/sync format for browser form workflows. |
| [XFDF](https://www.nutrient.io/guides/web/forms/fill-form-fields/import-from-xfdf.md)                                         | You need interoperability with external PDF tools.                                |
| [Document Engine with Instant synchronization](https://www.nutrient.io/guides/web/forms/submit-or-save/to-server-backed.md) | You need collaborative, multiuser form workflows across sessions/devices.         |

For an end-to-end authoring workflow, refer to the [building a browser form template builder](https://www.nutrient.io/guides/web/forms/browser-form-template-builder.md) guide.
---

## Related pages

- [Supported PDF form fields](/guides/web/forms/introduction-to-forms.md)
- [Understanding the benefits of PDF forms](/guides/web/forms/introduction-to-forms/what-are-forms.md)