RSL (Really Simple Licensing) — agent readiness

A License line in robots.txt pointing at an XML licence that says on what terms AI systems may use the content.

Why an agent cares

It turns a yes-or-no crawl rule into terms: what AI systems may do with the content, and on what conditions, in a file crawlers already read. A crawler that cannot get a valid licence must treat the content as unlicensed, so a broken one gives away nothing it meant to grant and protects nothing it meant to reserve.

Adoption

Early production. Several independent organisations run it in production, though it is still niche on the open web.

Direction of travel: ▲ rising, as at 2026-10-14.

RSL 1.0 became a Recommendation on 2025-12-10, edited by the RSL Collective with Condé Nast, Ziff Davis and Schema.org. Stack Overflow and Medium publish License lines, and Google's Lighthouse stopped calling the directive unknown on 2026-10-09.

Adopter	Depth	Evidence
Stack Overflow	`production`	stackoverflow.com
Medium	`production`	medium.com

What we check

Absence is never a finding. Every check below runs only when this technology is detected, so a site that has not adopted this is not assessed on it and appears in no report. 7 of these 8 can fail it. In Lumar these appear once per site, in the site-wide results of each crawl.

Check	Severity	Raises	On whose authority
RSL License Not Absolute	high	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: a License line in robots.txt gives a relative address such as /license.xml, but it must be a full URL, so crawlers can't reliably find the licence. Fix: write License: https://example.com/license.xml.
RSL License Unreachable	high	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: the licence a License line points at answered that it isn't there (for example 404), so crawlers find no licence and treat the content as unlicensed. Fix: publish the licence at that address, or point the line at where it is.
RSL Malformed XML	high	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: the licence file isn't well-formed XML (an element that never closes), so a crawler can't read its terms. Fix: validate the file and close every element.
RSL Wrong Namespace	high	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: the licence's root isn't <rsl> with the RSL 1.0 namespace as its default namespace (an older draft namespace or a prefix instead), so crawlers that identify licences by namespace don't recognise it. Fix: start the file with <rsl xmlns="https://rslstandard.org/rsl">.
RSL Missing Content	medium	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: the licence has no <content> element, so it licenses nothing. Fix: add <content url="/"> with a <license> inside it.
RSL Content Missing URL	medium	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: a <content> element has no url attribute, so a crawler can't tell which content the licence covers. Fix: add one, e.g. <content url="/"> for the whole site.
RSL Content Missing License	medium	conformance, usability	specification: Really Simple Licensing (RSL) 1.0 Specification
Supporting documents: Really Simple Licensing (RSL) 1.0 Specification Required by Really Simple Licensing (RSL) 1.0 Specification. Bad: a <content> element has no <license> inside it (terms on their own are not a licence), so the content it names stays unlicensed. Fix: add a <license> with what you permit, e.g. <license><permits type="usage">ai-train</permits></license>.
RSL Partially Assessed	coverage note	nothing	our own coverage

Examples

Both run through the same checks as a live scan: the first passes, the second is flagged.

correctxml

<?xml version="1.0" encoding="UTF-8"?>
<rsl xmlns="https://rslstandard.org/rsl">
  <content url="/">
    <license>
      <permits type="usage">search</permits>
      <prohibits type="usage">ai-train</prohibits>
    </license>
    <terms>https://example.com/terms</terms>
  </content>
</rsl>

present but wrongxml

<?xml version="1.0" encoding="UTF-8"?>
<rsl xmlns="https://rslstandard.org/rsl">
  <content>
    <license>
      <permits type="usage">search</permits>
    </license>
  </content>
  <content url="/blog/">
    <terms>https://example.com/terms</terms>
  </content>
</rsl>

Specifications

Document	Revision	Kind
Really Simple Licensing (RSL) 1.0 Specification	RSL-SPEC-1.0, Recommendation, 2025-12-10	specification

Last re-read against the published documents: 2026-10-14.