Add support for approximate geolocation #195

alvinjiooo · 2025-09-05T01:37:19Z

This commit introduces the ability for users and developers to request a less precise, privacy-preserving "approximate" location.

Key changes include:

A new accuracyMode option in PositionOptions to request either "precise" or "approximate" location.
A new geolocation-approximate permission and policy, which is implicitly granted if the "geolocation" permission is given.
Separate internal caching for precise and approximate positions.
Updated "Request a position" and "Acquire a position" algorithms to handle the new accuracy levels, permission fallback, and caching logic.
The GeolocationPosition interface now includes an accuracyMode attribute to reflect the accuracy of the returned position.
Expanded the introduction with a non-normative description of what an "approximate location" is.
Added a normative privacy requirement for user agents to mitigate precise location reconstruction by caching approximate locations for a period of time.

Closes #182

Approximate Geolocation explainer

Preview | Diff

This commit introduces the ability for users and developers to request a less precise, privacy-preserving "approximate" location. Key changes include: - A new `accuracyMode` option in `PositionOptions` to request either "precise" or "approximate" location. - A new `geolocation-approximate` permission and policy, which is implicitly granted if the "geolocation" permission is given. - Separate internal caching for precise and approximate positions. - Updated "Request a position" and "Acquire a position" algorithms to handle the new accuracy levels, permission fallback, and caching logic. - The `GeolocationPosition` interface now includes an `accuracyMode` attribute to reflect the accuracy of the returned position. - Expanded privacy and user consent sections to discuss the benefits and user interface implications of approximate location.

…tion

nondebug · 2025-09-05T19:06:47Z

index.html

      </p>
+      <p>
+        To better protect user privacy, this specification also provides a way
+        for users to share an <em>approximate location</em> instead of a


We should define all our terms here with <dfn> tags so we can refer back to them elsewhere in the spec.

I think we should define "approximate location" in a way that makes it clear it's an optional thing that some location sources support and some don't. The previous paragraph refers to "sources of location information", I think we should turn it into a proper definition and refer to it here.

Perhaps:

An <dfn>approximate location information source</dfn> is a [=location information source=] that returns positions that have been intentionally obfuscated to make it more difficult to recover the true location.

Currently I added precise position and approximate position and approximate location information source to the introduction chapter. PTAL

index.html

reillyeon · 2025-09-09T22:59:16Z

For readability as you iterate on this proposal it's okay for this PR to directly change the specification text however to land this change the changes need to be enclosed in the correct candidate additions/corrections/deletions syntax.

marcoscaceres · 2025-09-11T09:43:50Z

@reillyeon if it's ok, let's move this to CR first (i.e., let's not waste time with the ins/dels). We are close to publishing as CR again.

index.html

antosart · 2025-09-18T07:16:20Z

index.html

        <aside class="example" title="Permissions Policy over HTTP">
          <pre class="http">
-            Permissions-Policy: geolocation=()
+            Permissions-Policy: geolocation=(), geolocation-approximate=()


What about just writing

Permissions-Policy: geolocation-approximate=()

here and explaining in words that by disabling geolocation-approximate, geolocation will automatically be disabled too?

index.html

antosart · 2025-09-18T07:24:30Z

index.html

+          permission|checks permission=] for the level of accuracy specified by
+          the {{PositionOptions/accuracyMode}} option. A grant for the
+          "geolocation" permission implies a grant for the
+          "geolocation-approximate" permission.


I would add

"while if the "geolocation-approximate" is denied, then so is "geolocation""

antosart · 2025-09-18T07:30:45Z

index.html

+          "geolocation-approximate" permission.
        </p>
        <p>
          When <dfn data-local-lt="check permission">checking permission</dfn>


I think we'll want to expand this and clarify that when requesting permission to use geolocation, the user will also be prompted for geolocation-approximate. This will probably require some changes to https://www.w3.org/TR/permissions/#dfn-request-permission-to-use so that that algorithm can be overridden, and we'll need to override it here.

Do you mean we should add the case when website request position using accuracy_mode='approximate', the prompt should show approximate option and denial only?

No, I mean that when the website requests position using accuracy_mode='precise', then the browser should show a prompt that allows the user to either grant precise location or approximate location. So a request for precise location might end up changing the values of both the geolocation and geolocation-approximate permissions.

For how things work at the moment in the spec, two different powerful features are independent from each other and you can either prompt for one or for the other. I think we want some mechanism so that the prompts for the two features geolocation and geolocation-approximate are intertwined.

Thanks for clarification, I added a new for "request geolocation permission" to describe the interaction between "geolocation" and "geolocation-approximate", also use it in "Request a position". Please review this part see if this make more sense now.

index.html

Copilot

Pull Request Overview

This PR adds support for approximate location positioning to the Geolocation API specification. It introduces a privacy-preserving alternative to precise location sharing, allowing applications to request coarse-grained location data when high accuracy is not needed.

Key changes:

Introduces accuracyMode option with "precise" (default) and "approximate" values
Adds new "geolocation-approximate" permission alongside existing "geolocation" permission
Implements separate caching for precise and approximate positions
Updates permission request flows to allow users to choose between precise and approximate location sharing

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Copilot · 2025-10-29T06:44:07Z

index.html

+                  <li>Go to <a href="#errors-reasons">dealing with
+                  failures</a>.


The link references #errors-reasons, but this section ID no longer exists in the document. The 'Dealing with failures' section appears to have been removed during the refactoring. This broken link should either be removed or updated to reference the correct error handling section, or the id=\"errors-reasons\" anchor should be restored.

Suggested change

<li>Go to <a href="#errors-reasons">dealing with

failures</a>.

<li>Go to dealing with failures.

Copilot · 2025-10-29T06:44:08Z

index.html

                  <li>Do the <a href="#permission-denied">user or system denied
                  permission</a> failure case step.


The link references #permission-denied, but this section ID no longer exists in the document. The 'User or system denied permission' section appears to have been removed during the refactoring. This broken link should either be removed or updated to reference the correct error handling, or the id=\"permission-denied\" anchor should be restored.

Suggested change

<li>Do the <a href="#permission-denied">user or system denied

permission</a> failure case step.

<li>Handle the user or system denied permission failure case.

Copilot · 2025-10-29T06:44:08Z

index.html

+          <tr>
+            <td>
+              <del><dfn data-dfn-for=
+              "Geolocation">[[\cachedPosition]]</dfn></del>
+            </td>
+            <td>
+              <del>A {{GeolocationPosition}}, initialized to null. It's a
+              reference to the last acquired position and serves as a cache. A
+              user agent MAY evict {{Geolocation/[[cachedPosition]]}} by
+              resetting it to null at any time for any reason.</del>
+            </td>
+          </tr>
          <tr>
            <td>


The deprecated [[cachedPosition]] internal slot is marked with <del> tags but is still present in the specification table. This entry should be completely removed rather than shown as deleted text in the final specification, as it may confuse readers about what is actually part of the current API.

Suggested change

<tr>

<td>

<del><dfn data-dfn-for=

"Geolocation">[[\cachedPosition]]</dfn></del>

</td>

<td>

<del>A {{GeolocationPosition}}, initialized to null. It's a

reference to the last acquired position and serves as a cache. A

user agent MAY evict {{Geolocation/[[cachedPosition]]}} by

resetting it to null at any time for any reason.</del>

</td>

</tr>

<tr>

<td>

<tr>

<td>

Copilot · 2025-10-29T06:44:08Z

index.html

+                  <li>Let |positionData| be a [=map=] with the following
+                  name/value pairs based on the acquired position data:
+                    <dl>
+                      <dt>


The positionData map is missing the required "latitude" field. The specification defines longitude, altitude, accuracy, altitudeAccuracy, speed, and heading, but does not include latitude, which is a fundamental coordinate required for geolocation.

Suggested change

<dt>

<dt>

"latitude"

</dt>

<dd>

A {{double}} that represents the latitude coordinates

on the Earth's surface in degrees, using the [[WGS84]]

coordinate system. Latitude measures how far north or

south a point is from the Equator.

</dd>

<dt>

Alvin Ji added 3 commits September 4, 2025 18:33

fixup! Add support for approximate geolocation

78c9dac

Docs: Add description and privacy considerations for approximate loca…

24484bc

…tion

alvinjiooo requested a review from nondebug September 5, 2025 18:25

chore: Tidy HTML

b2d9d85

nondebug reviewed Sep 5, 2025

View reviewed changes

fix: Address all outstanding review comments

07711d6

chore: Tidy HTML

5c9f878

jyasskin mentioned this pull request Sep 12, 2025

Approximate Geolocation w3ctag/design-reviews#1131

Closed

2 tasks

alvinjiooo mentioned this pull request Sep 12, 2025

Approximate geolocation WebKit/standards-positions#470

Closed

antosart reviewed Sep 18, 2025

View reviewed changes

Alvin Ji added 3 commits September 19, 2025 15:49

fix: Address review comments

11c6d13

fix: Address review comment

9578188

feat: Define custom permission flow for geolocation

3fa8869

alvinjiooo force-pushed the add-approximate-geolocation branch from 99d9b03 to 3fa8869 Compare September 22, 2025 22:49

marcoscaceres added the TPAC2025 Topics for discussion at TPAC 2025 label Oct 28, 2025

marcoscaceres requested a review from Copilot October 29, 2025 06:42

Copilot AI reviewed Oct 29, 2025

View reviewed changes

		<li>Go to <a href="#errors-reasons">dealing with
		failures</a>.

	<li>Go to <a href="#errors-reasons">dealing with
	failures</a>.
	<li>Go to dealing with failures.

		<li>Do the <a href="#permission-denied">user or system denied
		permission</a> failure case step.

	<li>Do the <a href="#permission-denied">user or system denied
	permission</a> failure case step.
	<li>Handle the user or system denied permission failure case.

-                      <dt>
+                      <dt>
+                        "latitude"
+                      </dt>
+                      <dd>
+                        A {{double}} that represents the latitude coordinates
+                        on the Earth's surface in degrees, using the [[WGS84]]
+                        coordinate system. Latitude measures how far north or
+                        south a point is from the Equator.
+                      </dd>
+                      <dt>

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alvinjiooo commented Sep 5, 2025 •

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