Eye Tracking in Unity¶

Status: emerging
Last updated: 2026-06-01
Sources: Unity Eye Tracking Sdk Overview, Sranipal Framework Overview, Godot Openxr Eye Gaze Interaction Extension, Tobii Ocumen Overview
Tags: [unity, eye-tracking, openxr, sranipal, tobii, varjo, meta, pupil-labs, sdk]

Summary¶

Unity has the broadest eye-tracking SDK coverage of the three engines surveyed, spanning a native OpenXR path and several vendor SDKs. The native Unity OpenXR plugin exposes only combined gaze via XR_EXT_eye_gaze_interaction, while richer data comes from vendor SDKs: HTC SRanipal, Tobii Ocumen, Pupil Labs Neon XR, the Meta XR SDK, and the Varjo XR plugin (Anonymous, 2026). The Varjo plugin is described as the research gold standard, exposing calibrated millimetre pupil and iris diameter, nanosecond timestamps, and 200 Hz raw streams that no other Unity integration matches (Anonymous, 2026). No eye-tracking API is restricted by Unity's license tier, and the runtime fee was permanently cancelled in September 2024.

Body¶

Context¶

This article combines three sources on Unity's eye-tracking options: an unverified web-search digest of Unity eye-tracking SDKs and plugins (Anonymous, 2026), HTC's SRanipal framework overview (HTC Corporation, 2026), and the OpenXR XR_EXT_eye_gaze_interaction specification (Khronos Group, 2026). They are technical feature digests describing the native OpenXR path, the vendor SDKs that exceed it, and Unity's licensing terms. Within this knowledge base this is the Unity arm of the per-engine eye-tracking survey: it builds on the shared baseline in Openxr Eye Gaze Interaction, draws on the dedicated Sranipal Sdk article for the HTC path, sits beside its Unreal Eye Tracking and Godot Eye Tracking counterparts, and feeds the cross-engine ranking in Eye Tracking Engine Comparison, where Unity comes out ahead on data depth and research reliability. Each point below is attributed to its source.

Key Points¶

Unity's baseline is the same portable floor every engine shares. Anonymous (2026) report that the Unity OpenXR Plugin (com.unity.xr.openxr, v1.15.1) exposes XR_EXT_eye_gaze_interaction through its EyeGazeInteraction feature, providing a combined binocular gaze pose and a validity flag, with no per-eye, pupil, blink, openness, or high-frequency raw data; confirmed headsets for this path include HoloLens 2, Vive Pro Eye via SteamVR OpenXR, Varjo XR-3/XR-4, Pico 4 Enterprise, and Meta Quest Pro (the latter via OVRPlugin rather than native OpenXR) (§ 1. Unity Native OpenXR — EyeGazeInteraction). These capabilities and limits match the Khronos Group (2026) specification described in Openxr Eye Gaze Interaction, so anything beyond gaze direction requires a vendor SDK.

For HTC hardware, SRanipal remains the feature-rich option but carries the deprecation risk detailed in Sranipal Sdk. Anonymous (2026) state that in Unity, SRanipal v1.3.6.8 supports Unity 2019–2022 (untested on Unity 6) and exposes data OpenXR cannot — combined and per-eye gaze, normalized 0–1 pupil diameter, normalized openness, blink, 2D sensor pupil position, and gaze origin at 120 Hz — through a Windows runtime service reached over a local pipe (§ 2. HTC SRanipal SDK in Unity). VRCFaceTracking Project (2026) confirm that these pupil values are normalized rather than calibrated millimetres, so they cannot support absolute pupillometry without device-specific calibration (§ Key Limitations), and that HTC recommends migrating new projects to VIVE OpenXR with XR_HTC_eye_tracker (§ Migration Recommendation (HTC Official)).

Research-grade vendor SDKs differ sharply in data quality and hardware reach. Tobii Ocumen is Tobii's XR research SDK providing advanced eye-tracking data for Unity developers (Tobii AB, 2026). It exposes per-eye gaze rays, per-eye pupil diameter, position guides, system and device timestamps, combined gaze vector, and blink detection through three modules: Configuration (calibration/setup), Advanced Signals (raw data), and Filters (signal processing). However, device support is severely limited to only the Pico Neo 3 Pro Eye and Play for Dream MR — no Vive, Varjo, or Quest hardware is supported (Tobii AB, 2026). Access requires contacting Tobii for licensing. Tobii Pro SDK v2.0 removed all VR/HMD support in 2024, leaving Ocumen as the only Tobii VR path (Anonymous, 2026). Pupil Labs Neon XR is an open-source package for the standalone Neon module that mounts on Quest 3, Pico 4, or other headsets and streams 3D gaze, 2D gaze point, built-in fixation detection, blink, estimated pupil diameter, and 200 Hz raw samples over the local network via the Neon Companion App (§ 4. Pupil Labs Neon XR (Unity)). The Meta XR SDK (v69+) exposes per-eye gaze pose, confidence, and tracked state through OVREyeGaze on Quest Pro, but no pupil, blink, or openness through that API — openness lives in the separate Face Expressions SDK (§ 5. Meta XR SDK — Quest Pro Eye Tracking).

The Varjo XR plugin is presented as the strongest research integration in any engine (Anonymous, 2026). The open-source (Apache 2.0) com.varjo.xr package (v3.7.3, Unity 6 support from v3.7.0) on Varjo XR-4/XR-3/VR-3 exposes per-eye and combined gaze rays, gaze forward/up vectors, focus distance, calibrated millimetre pupil diameter, calibrated millimetre iris diameter, openness, nanosecond timestamps, selectable 100/200 Hz sampling, and independently accessible raw and smoothed streams (§ 6. Varjo XR Plugin for Unity (Best for Research)). The digest states this combination — especially calibrated mm pupil and iris diameter, nanosecond timestamps, and 200 Hz — is not matched by any other VR headset plus Unity integration; because this is a single-source superlative it is treated as emerging. The broader comparative judgement is examined in Eye Tracking Engine Comparison.

Licensing imposes no eye-tracking constraint (Anonymous, 2026). The Unity runtime fee was permanently cancelled (September 2024); Personal is free up to $200K annual revenue/funding, Pro is $2,310/seat/year above that, and Enterprise is custom above $25M, with a free Education Grant License for qualifying institutions. No XR or OpenXR feature, including any eye-tracking API, is tier-restricted, so all of the above are available on the free Personal tier subject only to hardware cost (§ 7. Unity Licensing Summary).

Conclusion¶

Across these sources Unity has the broadest eye-tracking coverage of the three engines: a portable OpenXR floor (Khronos Group, 2026), HTC's feature-rich but deprecating SRanipal (HTC Corporation, 2026), and a spread of vendor SDKs topped by the Varjo plugin, which the digest singles out as the research gold standard for calibrated-mm and 200 Hz data (Anonymous, 2026). Licensing adds no constraint. The principal qualifications are the deprecation risk around SRanipal and the single-source, emerging status of the Varjo superlative.

References¶

Anonymous (2026) Eye Tracking in Unity — SDK and Plugin Overview (Web Search Digest). Research digest, virtual-environments-kb RAW (Accessed: 31 May 2026). unityEyeTrackingOverview2026

Khronos Group (2026) XR_EXT_eye_gaze_interaction — OpenXR Specification. Available at: https://registry.khronos.org/OpenXR/specs/1.0/html/xrspec.html#XR_EXT_eye_gaze_interaction (Accessed: 31 May 2026). khronos2026eyegaze

Tobii AB (2026) Tobii Ocumen — XR Eye Tracking SDK Overview. Tobii Developer Documentation. Available at: https://developer.tobii.com/xr/ocumen/overview/ (Accessed: 1 June 2026). tobiiOcumen2026

VRCFaceTracking Project (2026) SRanipal — VIVE Hardware Documentation. VRCFaceTracking Docs. Available at: https://docs.vrcft.io/docs/v4.0/hardware/VIVE/sranipal (Accessed: 1 June 2026). vrcftSranipal2026

Open Questions¶

Does SRanipal work on Unity 6? Community reports are mixed and HTC has not tested it (Anonymous, 2026).
Is the Varjo "best in any engine" data-quality claim independently confirmed, or does it rest only on this digest?