---
title: "What is image segmentation?"
description: "Image segmentation labels the pixels or regions that belong to an object or a prompt, rather than only a bounding box."
url: "https://pixeltable.com/learn/what-is-image-segmentation"
updated: "2026-09-29"
vertical: "Vision"
doc: "https://docs.pixeltable.com/platform/type-system"
---

# What is image segmentation?

Image segmentation labels the pixels or regions that belong to an object or a prompt, rather than only a bounding box.

Updated: 2026-09-29
Part of [What is computer vision?](https://pixeltable.com/learn/what-is-computer-vision).

## On this page

- [How it works](https://pixeltable.com/learn/what-is-image-segmentation#how-it-works)
- [What it is not](https://pixeltable.com/learn/what-is-image-segmentation#what-it-is-not)
- [Comparison](https://pixeltable.com/learn/what-is-image-segmentation#comparison)
- [Where Pixeltable fits](https://pixeltable.com/learn/what-is-image-segmentation#where-pixeltable-fits)
- [Questions](https://pixeltable.com/learn/what-is-image-segmentation#questions)

## How it works {#how-it-works}


- A model reads the image and an optional prompt.
- It writes a mask.
- The mask is stored on the row so later steps can crop or measure.

## What it is not {#what-it-is-not}

It is not detection boxes, and it is not a consumer background-removal filter that stores no mask.

## image segmentation: this, and the thing it is confused with {#comparison}

|  | This | Not this |
| --- | --- | --- |
| Output | A mask | A box |
| Prompt | Optional text or points | Always a fixed class list |
| Use | Cut out, measure, or train | Draw a rectangle |

## Where Pixeltable fits {#where-pixeltable-fits}

Pixeltable stores the mask as a computed column on the image row. Promptable models such as SAM follow that pattern.

## Questions {#questions}

### How does image segmentation work? {#faq-1}

A model reads the image and an optional prompt. It writes a mask. The mask is stored on the row so later steps can crop or measure.

### What is image segmentation often confused with? {#faq-2}

It is not detection boxes, and it is not a consumer background-removal filter that stores no mask.

## In the blog

- [SAM 3 Promptable Segmentation in Pixeltable](https://pixeltable.com/blog/sam3-promptable-segmentation-pixeltable)
- [Pixeltable July 2026 release: SAM 3, Nano Banana, Nebius, and an agent-friendly column API](https://pixeltable.com/blog/pixeltable-july-2026-release-highlights)

## Related

- [Documentation](https://docs.pixeltable.com/platform/type-system)
- [SAM 3 Promptable Segmentation in Pixeltable](https://pixeltable.com/blog/sam3-promptable-segmentation-pixeltable)
- [background-remover](https://pixeltable.com/background-remover)
- [magic-eraser](https://pixeltable.com/tools/magic-eraser)