Let’s be direct upfront: if you’re building an indie game, we strongly recommend avoiding complex probability-based monetization systems to begin with. The regulatory compliance burden is substantial, and for small teams, the risk-to-reward ratio is poor.
That said, if your game includes gacha mechanics — particularly common in idle RPGs and similar mobile-adjacent games — Korean law requires specific disclosure practices that catch many developers off guard. The Korea Game Rating and Administration Committee (게임물관리위원회, GRAC) has been actively monitoring games and issuing correction orders. Here’s what the violation data from 2024-2025 monitoring shows you need to know.
Basic Principles for Disclosure of Probability Information — If the game I service includes probability-type items, users must be able to calculate the accurate expected value before purchasing such items through the displayed information. Categories of Probability Disclosure Obligations: Games · Internet Websites · Advertisements and Promotional Materials (Act on Promotion of Game Industry)
Probability information must be displayed not only on the game and website but also on all advertisements and promotional materials promoting the game. This includes video advertisements, streamer advertisements, and social media image advertisements.
While general probability information is displayed, a common violation involves the omission of probabilities for certain content or specific items. Therefore, you must thoroughly check to prevent errors such as missing package components, unupdated short-term events, failure to display dice, roulette, or bingo items, failure to display pity rewards, or inability to access linked pages.
Probability information must be displayed not only on the game and website but also on all advertisements and promotional materials promoting the game. This includes video advertisements, streamer advertisements, and social media image advertisements.
Pity Reward Precautions — If the structure involves providing one item from among several items of the same grade rather than ‘guaranteedly one type’ of a specific item through the pity reward, you must also indicate the probability of each item being provided.
Ex) “Guaranteed SS character upon 100 attempts” → Need to display the list of SS characters and the probability for each character
Even if the components of probability-type items are grouped into the same grade, each item, option, and quantity may actually have different probabilities. It is inappropriate to disclose only the sum of probabilities by grade or to provide guidance using range values such as ‘A~B’.
If it is a system where probability changes under specific conditions, you must provide information on the probability situation before and after the change. You must specify the clearly changed numerical value rather than using abstract phrases such as ‘probability UP’.
Probabilities must be expressed as ‘percentages’; however, if it is difficult to display all digits, they must be rounded to at least four decimal places lower than the first non-zero digit. Arbitrarily determining the number of decimal places makes it difficult to compare subtle differences in probability.
The sum of the probability notations must be 100%, and all items must be displayed as a single number. Range and inequality notations such as ‘<1%’ or ‘0.3%~0.7%’ are inappropriate as they indicate actual probabilities only at an estimated level.
Probability values and the names of the items involved must always be presented accurately and consistently. Discrepancies frequently occur when only one side is modified after probability adjustments or due to translation errors.
The Basic Principle
If your game contains probability-based items, players must be able to calculate precise expected values from your disclosed information before making any purchase. This isn’t a soft recommendation — it’s the legal standard under Korea’s Game Industry Promotion Act (「게임산업진흥에 관한 법률」).
The disclosure obligation covers three channels simultaneously: the game itself, your official website, and all advertising and promotional materials. All three must display probability information. This means YouTube ads, sponsored streamer content, and social media image posts all require probability disclosure — not just the in-game shop screen.
Where Developers Most Commonly Go Wrong
GRAC’s monitoring identified specific violation patterns that keep appearing. Understanding these helps you audit your own disclosure:
Missing items within disclosed systems. The most common violation isn’t failing to disclose any probabilities — it’s disclosing most probabilities while accidentally omitting specific items. Package contents listed incompletely, short-term event items that weren’t added to probability tables, minigame mechanics (dice, roulette, bingo) that weren’t treated as probability items requiring disclosure, and broken or inaccessible links to probability pages all qualify as violations.
Pity system (천장) disclosure errors. This is where many developers make conceptually serious mistakes. If your pity system guarantees “1 SS character at 100 pulls” but that guarantee draws from a pool of multiple SS characters rather than a single specific item, you must display the individual probability for each character within that guarantee pool. Simply stating “SS character guaranteed at 100 pulls” is insufficient if multiple SS characters exist with different individual drop rates within that guarantee.
Additionally, if you have a pity system, you cannot only display the combined probability that factors in pity activation. You must separately display both the base rate and the rate when pity triggers. These are different numbers, and both must appear.
The Precision Requirements
The precision rules exist because developers left to their own devices tend to round numbers in ways that make small probability differences invisible to players.
Probabilities must be displayed as percentages. When full decimal precision isn’t practical, the rounding rule is specific: round no earlier than four digits below the position of the first non-zero digit. This means a 0.01% chance cannot be displayed as simply “0%” or “<1%”.
All probabilities for a given banner or pool must sum to exactly 100%. All values must be expressed as single numbers — not ranges. “<1%”, “0.3%~0.7%”, and similar approximate expressions are explicitly non-compliant. Either you know the number or the display is wrong.
The same item names and probability values must appear identically across all disclosure locations. A surprisingly frequent violation occurs when a probability is adjusted in-game, but the website isn’t updated simultaneously, or when translation errors create discrepancies between Korean and English displays.
Additional conditional probability requirement. If any system in your game changes probabilities based on conditions — “rate UP” events, pity building, special conditions — you must display both the before and after numbers with explicit numerical values. “Rate UP!” as explanatory text is not sufficient. The specific changed percentage must appear.
A Self-Audit Checklist
Before launch or before any gacha update, verify the following across the game, website, and all active advertising:
- Every item in every probability pool is listed individually with its specific percentage
- Pity/guarantee systems show both base rates and pity-triggered rates as separate figures
- When pity draws from a pool rather than giving a single guaranteed item, every item in that pool has its individual rate displayed
- All probability values in any given pool sum to 100%
- No ranges, no inequalities, no approximate expressions
- Precision follows the four-digit rule
- Item names match exactly between the game client and the website
- All promotional materials (video ads, streamer content, social posts) display probability information
- Short-term events and rate-UP events are updated across all three channels simultaneously
Where to Get Clarity
If you’re uncertain whether a specific system design is compliant, GRAC operates a dedicated business inquiry channel specifically for probability disclosure questions. Consulting this before launch is significantly better than receiving a correction order after.
Business inquiry contact:
Email: grac_lbguide@grac.or.kr
Phone: 051-720-4260
Required information in your inquiry: your name, affiliation, company name, game title, and the specific question — including the relevant legal provision or guidebook page reference if applicable.
GRAC provides a downloadable business inquiry form, or you can write a similar format in an email without the form. A violation case collection document covering 2024-2025 monitored games is also available from GRAC; note that the examples in that document use reconstructed fictional content rather than actual game names.
The Practical Recommendation
For most indie developers building games with small teams and limited legal resources, complex gacha monetization structures create regulatory exposure that’s difficult to manage properly. The compliance requirements are not ambiguous or arbitrary — they’re designed to ensure players can make genuinely informed purchase decisions — but they do require ongoing maintenance every time any probability is changed, every time a new event runs, and across every promotional channel you use.
If you’re committed to probability-based monetization, treat the disclosure requirement not as a compliance checkbox but as a design constraint from the start. Build your systems so that complete, accurate disclosure is a natural output of the system design rather than something that has to be manually reconstructed from complex backend logic. The violation patterns GRAC identified are almost all maintenance failures — systems that were disclosed at launch but not properly updated — which suggests that building disclosure into your operational workflow is as important as the initial implementation.
When in doubt, the business inquiry channel exists specifically for questions like yours. Using it before launch is the right move.
This article is based on GRAC monitoring data from 2024-2025 and the agency’s published guidance on probability information disclosure. Regulations may be updated; verify current requirements directly with GRAC before implementing probability-based systems.
