GLI-28 v1.0 Player User Interface Systems: Scope and Real Limits

GLI-28 Player User Interface Systems, Version 1.0 (14 February 2011), certifies the hardware and software that serve content to a System Window on a gaming device. It does not contain requirements for balance display, responsible gambling messaging, loss limit presentation or spin speed on online games. Those obligations sit in GLI-19 v3.0 and in regulator rules, and a GLI-28 certificate does not evidence them.

The standard applies to suppliers of PUI systems, meaning the overlay and secondary-content layers that run beside or over a certified game. Licensees that treat GLI-28 as the online game UX standard are working from a mistaken premise.

What does GLI-28 v1.0 actually certify?

GLI-28 v1.0 defines a Player User Interface (PUI) System as all hardware and software associated with serving content to the System Window (section 1.2.6). The Game Window shows base game content controlled by the gaming device’s main processor board (section 1.2.4). The System Window shows content controlled and sent from an outside system (section 1.2.5). Both may share the same physical display devices. The standard also defines a Resized Window (section 1.2.7) and an Overlay Window (section 1.2.8).

The vocabulary, including “game monitor”, “gaming device prototype certification” and attendant retraction of a window during a tilt diagnosis, is that of a cabinet-based gaming device connected to an outside system.

Section 3.1.1 allows a System Window to be displayed, initiated or retracted at the player’s request at any time, and resized or overlay windows must let the player or an attendant retract them. Section 3.2.1 requires any resizing or overlay of the Game Window to be mapped accurately to the revised display and touch screen. Section 3.2.3 requires the PUI System to monitor and recall whether a system window was open at a specific time interval, without having to reproduce the sequence exactly as the player saw it.

“The PUI System shall not alter the content, play, color or functionality of the Game Window unless specifically submitted, reviewed and approved on a per game program basis.” GLI-28 v1.0, section 3.2.2.

How is GLI-28 assessed and evidenced?

A supplier submits the PUI System, and Gaming Laboratories International issues a certificate of compliance to the standard on certification, as the “About this Standard” page states. Chapter 2 lists the submission items, including source code for any re-mapping of the Game Window display program or component, software verification procedures and tools where these are not industry standard, and the tools needed to validate the standard’s requirements.

Chapter 4 sets security requirements for PUI systems used in non-marketing applications. The general note to section 4.1 states that it applies where the PUI system is intended for advanced content, including secondary wagering games. In practice, a PUI system carrying only marketing content faces a lighter test scope than one carrying wagering functionality. Section 3.2.2 also works as a change-control boundary: any overlay that touches the game display, such as a session clock drawn over a reel area, needs per-game approval.

Where do online game display obligations actually sit?

GLI-19 v3.0 (Interactive Gaming Systems) requires a player interface to display current funds available for wagering, denomination where applicable, current wager amount and placement of active wagers, wager options, and for the last completed game the outcome, amount won and wager options in effect. That information may be cleared early only if it remains available under game recall. Section 4.3.5 sets credit meter rules, including visibility whenever a wager may be placed and unambiguous credits or currency display. GLI-19 Appendix A allows self-imposed limits to be reduced only on 24 hours’ notice or as the regulatory body requires. GLI-11 v3.0 (section 4.2.2) and GLI-26 v2.0 carry separate player interface rules for their own device types.

Where do jurisdictions diverge on interface rules?

As of September 2026, the UKGC Remote gambling and software technical standards (RTS) were last updated on 12 January 2026. RTS 2E requires all gaming sessions to clearly display a customer’s net position, in the currency of the account, since the session started. RTS 14 (Responsible product design) sets the 2.5 second minimum game cycle for slots under 14D and a 5 second minimum for non-slots casino products under 14G. RTS 8 covers auto-play, which the UKGC’s consultation outcome confirmed is prohibited for online gaming products.

The 2.5 second rule has produced enforcement against a supplier. As reported in June 2026, Stakelogic BV agreed a £122,835 settlement with the UK Gambling Commission after Tiger Temple 88 ran with a 1.97 second gap between game cycles. A portfolio retest found 15 further games below the minimum, with shortfalls between 0.001 and 0.675 seconds, and the failure was attributed to reliance on manual stopwatch testing. In practice, a timing defect of this kind sits in game logic and front-end code, outside the scope of any GLI-28 test.

The AGCO Registrar’s Standards for Internet Gaming set the same 2.5 second interval in standard 2.18 and require the player to release and then depress the start button, or take equivalent action, for each cycle. Standard 2.19 bans features that let a customer reduce the time until the result is presented, such as turbo, quick spin and slam stop. Standard 2.21 requires a net position display in Canadian dollars for slots sessions. Ontario registrants should map deposit and loss limit tooling directly to the relevant Registrar’s Standards, since GLI-28 is silent on it.

The KSA Gaming System Assessment Scheme v2.1 (courtesy English translation, only the Dutch version binds) requires each accessible part of the player interface to show the current time in the Netherlands, the time elapsed since sign-in and the account balance.

What goes wrong in practice?

In practice, the recurring failure is a scoping error in the test plan. A supplier holds a GLI-28 certificate for an overlay product, and the licensee treats it as evidence that balance display, net position and cycle timing conform. For online games, interface conformity evidence should come from GLI-19 testing at the version the regulator accepts, plus regulator-specific tests against RTS 2E and 14D, AGCO standards 2.18 to 2.21, or the KSA scheme. Whether a given regulator accepts GLI-28 at all depends on its own technical standards, so licensees should take qualified legal counsel’s advice on jurisdiction-specific application and obtain the certificate’s scope statement and standard version from the laboratory.

This article rests on a direct reading of the GLI-28 v1.0 text, the GLI-19, GLI-11 and GLI-26 provisions cited, the UKGC RTS, the AGCO Registrar’s Standards and the KSA scheme v2.1. Readers comparing certification routes can also see GLI-19 vs GLI-33, the GLI certification hub and the UKGC RTS explorer.

Key Resources

GLI-28 Player User Interface Systems v1.0 (Gaming Laboratories International, 14 February 2011). GLI-19 Standards for Interactive Gaming Systems v3.0. UKGC Remote gambling and software technical standards, RTS 2, 8 and 14 (updated 12 January 2026). AGCO Registrar’s Standards for Internet Gaming, standards 2.18 to 2.21.

Matt Denney

Editorial · gamingcompliance.io

Reads the primary source so you don't have to. Fifteen years inside iGaming compliance: operator, supplier, and crown-corporation lottery.