---
title: "AutoTaggingEngine"
canonical_url: "https://www.nutrient.io/api/csharp/enums/auto-tagging-engine/"
md_url: "https://www.nutrient.io/api/csharp/enums/auto-tagging-engine.md"
last_updated: "2026-10-08T08:55:57.709Z"
description: "Selects the engine used to build the logical structure (tags) when converting a document to a tagged, accessible PDF (PDF/UA)."
---

Selects the engine used to build the logical structure (tags) when converting a document to a tagged, accessible PDF (PDF/UA).

```csharp

using Nutrient;

```

## Values

| Name                          | Value | Description                                                                                                                                                                                                                                                                                                                        |
| ----------------------------- | ----- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `AutoTaggingEngine.Heuristic` | `0`   | The built-in heuristic auto-tagger. Infers structure (headings, paragraphs, lists, tables, figures) from layout and font analysis. Fast and fully offline.                                                                                                                                                                         |
| `AutoTaggingEngine.Vision`    | `1`   | The Vision-based auto-tagger. Uses document layout segmentation, reading-order detection and table-structure recognition to build a higher-fidelity structure tree. Does not generate figure descriptions.                                                                                                                         |
| `AutoTaggingEngine.VisionVlm` | `2`   | The Vision-based auto-tagger with Vision Language Model enrichment. Adds generated alternate text for figures and summaries for charts on top of `Vision`. Requires a VLM provider to be configured (provider selection and credentials in the corresponding Vision settings); without one, tagging proceeds without descriptions. |

---

## Related pages

- [Enums](/api/csharp/enums.md)
- [Description Level](/api/csharp/enums/description-level.md)
- [Document Bookmark Source](/api/csharp/enums/document-bookmark-source.md)
- [Document Format](/api/csharp/enums/document-format.md)
- [Document Markup Mode](/api/csharp/enums/document-markup-mode.md)
- [Document Type](/api/csharp/enums/document-type.md)
- [Execution Provider](/api/csharp/enums/execution-provider.md)
- [Form Vlm Enrichment Model](/api/csharp/enums/form-vlm-enrichment-model.md)
- [Html Layout Type](/api/csharp/enums/html-layout-type.md)
- [Image Export Format](/api/csharp/enums/image-export-format.md)
- [Image Export Mode](/api/csharp/enums/image-export-mode.md)
- [Image Setting Mode](/api/csharp/enums/image-setting-mode.md)
- [Implicit Conversion](/api/csharp/enums/implicit-conversion.md)
- [Inline Style Reference Mode](/api/csharp/enums/inline-style-reference-mode.md)
- [Instant Json Render Theme](/api/csharp/enums/instant-json-render-theme.md)
- [Json Export Content](/api/csharp/enums/json-export-content.md)
- [Json Export Format](/api/csharp/enums/json-export-format.md)
- [Ocr Activation Mode](/api/csharp/enums/ocr-activation-mode.md)
- [Ocr Engine](/api/csharp/enums/ocr-engine.md)
- [Open Settings Mode](/api/csharp/enums/open-settings-mode.md)
- [Page Cache Mode](/api/csharp/enums/page-cache-mode.md)
- [Paper Normalization Mode](/api/csharp/enums/paper-normalization-mode.md)
- [Pdf Border Style](/api/csharp/enums/pdf-border-style.md)
- [Pdf Compression](/api/csharp/enums/pdf-compression.md)
- [Pdf Conformance](/api/csharp/enums/pdf-conformance.md)
- [Pdf Form Field Type](/api/csharp/enums/pdf-form-field-type.md)
- [Pdf Line Ending Style](/api/csharp/enums/pdf-line-ending-style.md)
- [Pdf Page Sizes](/api/csharp/enums/pdf-page-sizes.md)
- [Pdf Rubber Stamp Icon](/api/csharp/enums/pdf-rubber-stamp-icon.md)
- [Pdf Save Preferences](/api/csharp/enums/pdf-save-preferences.md)
- [Pdf Settings Mode](/api/csharp/enums/pdf-settings-mode.md)
- [Pdf Validation Conformance](/api/csharp/enums/pdf-validation-conformance.md)
- [Rendering Layout Mode](/api/csharp/enums/rendering-layout-mode.md)
- [Restoration Mode](/api/csharp/enums/restoration-mode.md)
- [Schema Compatibility](/api/csharp/enums/schema-compatibility.md)
- [Search Display](/api/csharp/enums/search-display.md)
- [Search Mode](/api/csharp/enums/search-mode.md)
- [Signature Certification Level](/api/csharp/enums/signature-certification-level.md)
- [Signature Format](/api/csharp/enums/signature-format.md)
- [Signature Hash Algorithm](/api/csharp/enums/signature-hash-algorithm.md)
- [Signature Key Source](/api/csharp/enums/signature-key-source.md)
- [Signature Level](/api/csharp/enums/signature-level.md)
- [Text Direction](/api/csharp/enums/text-direction.md)
- [Tiff Compression](/api/csharp/enums/tiff-compression.md)
- [Unit Mode](/api/csharp/enums/unit-mode.md)
- [Unparseable Output Handling](/api/csharp/enums/unparseable-output-handling.md)
- [Vision Engine](/api/csharp/enums/vision-engine.md)
- [Vision Features](/api/csharp/enums/vision-features.md)
- [Vision Output Format](/api/csharp/enums/vision-output-format.md)
- [Vlm Classification Strategy](/api/csharp/enums/vlm-classification-strategy.md)
- [Vlm Provider](/api/csharp/enums/vlm-provider.md)
- [Word Refining Method](/api/csharp/enums/word-refining-method.md)