Proximity Sensor

Editor’s Draft,

This version:
Latest published version:
Previous Versions:
Version History:
Feedback: with subject line “[proximity] … message topic …” (archives)
Issue Tracking:
Anssi Kostiainen (Intel Corporation)
Rijubrata Bhaumik (Intel Corporation)
Former Editor:
Dzung D Tran (Intel Corporation)
Bug Reports:
via the w3c/proximity repository on GitHub
Test Suite:
web-platform-tests on GitHub


This specification defines a concrete sensor interface to monitor the presence of nearby objects without physical contact.

Status of this document

This is a public copy of the editors’ draft. It is provided for discussion only and may change at any moment. Its publication here does not imply endorsement of its contents by W3C. Don’t cite this document other than as work in progress.

If you wish to make comments regarding this document, please send them to (subscribe, archives). When sending e-mail, please put the text “proximity” in the subject, preferably like this: “[proximity] …summary of comment…”. All comments are welcome.

This document was produced by the Device and Sensors Working Group.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 1 September 2015 W3C Process Document.

1. Introduction

The Proximity Sensor extends the Generic Sensor API [GENERIC-SENSOR] to provide information about proximity level, as detected by the device’s primary proximity sensor. The proximity level is reported as the distance (in centimeter) from the sensor to the closest visible surface. §6 Limitations of Proximity Sensors describes more about the potential limitations, why the precise distance value reported by different devices can be different, due to differences in detection method, sensor construction, etc. Moreover some proximity sensors might be only able to provide just a boolean to indicate if there is an object which is near, more like presence detection, than an absolute value for the distance.

2. Examples

let sensor = new ProximitySensor();

sensor.onchange = () => console.log(sensor.distance);

sensor.onerror = event => console.log(, event.error.message);

3. Security and Privacy Considerations

There are no specific security and privacy considerations beyond those described in the Generic Sensor API [GENERIC-SENSOR].

4. Model

The proximity sensor’s associated Sensor subclass is the ProximitySensor class.

The Proximity Sensor has a default sensor, which is the device’s main proximity detector.

A latest reading per sensor of proximity sensor type includes three entries whose keys are "distance", "max", "near" and whose values contain distance, max and near values.

The distance is a value that represents the distance between a device and the closest visible surface. Its unit is the centimeter (cm).

The max is a value that represents the maximum sensing range of the main proximity detector, in centimeters.

The near is a value that represent the presence of a visible surface in the vicinity of the main proximity detector.

5. API

5.1. The ProximitySensor Interface

[Constructor(optional SensorOptions sensorOptions)]
interface ProximitySensor : Sensor {
  readonly attribute unrestricted double? distance;
  readonly attribute unrestricted double? max;
  readonly attribute boolean? near;

To Construct a ProximitySensor Object the user agent must invoke the construct a Sensor object abstract operation.

5.1.1. The distance attribute

The distance attribute of the ProximitySensor interface represents the distance value. In other words, this attribute returns latest reading["distance"].

5.1.2. The max attribute

The max attribute of the ProximitySensor interface represents the max value. In other words, this attribute returns latest reading["max"].

5.1.3. The near attribute

The near attribute of the ProximitySensor interface represents the near value. In other words, this attribute returns latest reading["near"].

Note: If the implementation is unable to provide the near value, it could infer the near value from the value of distance. For example, if distance is not equal to max or default value (Infinity), it could imply there is an object in the sensing range.

6. Limitations of Proximity Sensors

Since most proximity sensors detect electromagnetic radiation (e.g., an infrared light or a magnetic field), certain material properties can interfere with the sensor’s ability to sense the presence of a physical object. Things that can interfere with a sensor include, but are not limited to, the material’s translucency, reflectiveness, color, temperature, chemical composition, and even the angle at which the object is reflecting the radiation back at the sensor. As such, proximity sensors should not be relied on as a means to measure distance. The only thing that can be deduced from a proximity sensor is that an object is somewhere in the distance between the minimum sensing distance and the maximum sensing distance with some degree of certainty.

7. Acknowledgements

Tobie Langel for the work on Generic Sensor API and inputs on this specification. Doug Turner for the initial prototype and Marcos Caceres for the test suite.

8. Conformance

Conformance requirements are expressed with a combination of descriptive assertions and RFC 2119 terminology. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC 2119. However, for readability, these words do not appear in all uppercase letters in this specification.

All of the text of this specification is normative except sections explicitly marked as non-normative, examples, and notes. [RFC2119]

A conformant user agent must implement all the requirements listed in this specification that are applicable to user agents.

The IDL fragments in this specification must be interpreted as required for conforming IDL fragments, as described in the Web IDL specification. [WEBIDL]


Terms defined by this specification

Terms defined by reference


Normative References

Tobie Langel; Rick Waldron. Generic Sensor API. URL:
Anne van Kesteren; Domenic Denicola. Infra Standard. Living Standard. URL:
S. Bradner. Key words for use in RFCs to Indicate Requirement Levels. March 1997. Best Current Practice. URL:
Cameron McCormack; Boris Zbarsky; Tobie Langel. Web IDL. URL:

IDL Index

[Constructor(optional SensorOptions sensorOptions)]
interface ProximitySensor : Sensor {
  readonly attribute unrestricted double? distance;
  readonly attribute unrestricted double? max;
  readonly attribute boolean? near;