This is an old thread, so this idea may have been already supposed:

Instead of having individual tags for content like "Drug usage", have different categories of content rated by the developer out of 5*, similar to how the site Common Sense Media† does it.

Each axis of rating should also have a word-limited textbox to clarify what content is in the game, again much like CSM. Coinciding with this is a list of tags oriented towards potential specific triggers, (e.g: self-harm, eating disorders, flashing lights, sexual harassment).

This should also integrate into a Content Warning Page, appearing when you click on a game for the first time before showing the game page. It would show the content ratings and associated clarifications, as well as the list of trigger tags, then requiring a confirmation to proceed to the game page.‡

*: possibly with an aggregate community rating shown side-by-side
†: who I have significant hang-ups with, but nonetheless
‡: a plausibly important coinciding change is to allow the report system to file for misrepresentative tags and ratings

It can also have IARC

So, was this implemented or not?

I think a content rating system for itch.io would be great, although if there is a new system for itch.io, it should somewhat follow the industry standards as seen in IARC in order to make the transition for developers as smooth as possible since a lot of them might sell their games on other storefronts or platforms such as Steam or the Nintendo eShop. Preferably, I'd like to see itch.io with the option to use IARC (ESRB/PEGI)/CERO ratings in addition to an itch.io built a system that works in a similar but simpler way. For that simplified system, using some ideas I've seen in this thread and from other rating systems that are in IARC, this is my idea for how an itch.io rating system could work out.

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Ratings

• Everyone
  • Intended for players ages 3-11
  • Similar to ESRB's Everyone, PEGI's 7, CERO's A (All Ages)
  • Mario Kart

• Teenage 
  • Intended for players ages 12-14
  • Similar to ESRB's Teen, PEGI's 12, CERO's C (Ages 15 and up)
  • The Legend of Zelda

• Mature 
  • Intended for players ages 16-17
  • Similar to PEGI's 16, CERO's D (Ages 17 and up)
  • Monster Hunter

• Adult/NSFW
  • Intended for players ages 18 and up
  • Similar to ESRB's Adults Only, PEGI's 18, CERO's Z (Ages 18 and up only)

I think 4 categories works out since each is distinct and easy to follow. Everyone represents games that are suitable for all ages and at most may have content that isn't suitable for extremely young children. Teenage (I think it should have a different name, maybe Moderate, but I can't come up with one) represents games that are suggestive or mild in terms of their content. Mature represents games that are realistic in their content but are otherwise moderate in their content. Adult/NSFW represents games that are clearly graphic or explicit in their content and should not be viewable by players that aren't 18 or older. 

Content Descriptors

Content Descriptors 

These broadly denote the type of content featured in a game and would be prominently featured on a games store page.

• Violence
  • Fighting or harmful action

• Graphic Content
  • Blood, gore, etc

• Sexual Content
  • Nudity, sexual activity, innuendos, etc

• Language
  • Swearing, expletives, etc

• Drugs, Alchohol, and Smoking
  • Depictions or use of drugs, alcohol, or tobacco products

• Distress
  • Frightful elements, horror, self-harm, etc

• Gambling 
  • Gambling, depictions of gambling, lootboxes, etc

Content Descriptor Tags

These are tags that go into specifics as to what type of content the game features within the descriptors themselves, and would be searchable just like the other metadata tags that are used for games currently.

• Violence
  • Fighting 
  • Dismemberment 
  • Exaggerated fictional violence 
  • Murder
  • Corpses

• Graphic Content
  • Blood
  • Gore

• Sexual Content
  • Suggestive clothing
  • Innuendos
  • Partial nudity
  • Nudity
  • Depictions of sexual activity

• Language
  • Mild language
  • Abusive language
  • Blasphemy

• Drugs, Alchohol, and Smoking
  • Drug use and reference
  • Drug reference 
  • Alchohol use and reference
  • Alchohol reference
  • Smoking use and reference
  • Smoking reference

• Distress
  • Occult characters (ghosts, zombies, etc)
  • Unsettling atmosphere/character design
  • Horrific sounds
  • Horrific graphical elements
  • Frightening surprise (jumpscares)
  • Self-harm
  • Depression 

• Gambling
  • Gambling reference
  • Lootboxes
  • Organized crime

The content descriptor and the content descriptor Tgas would be used together to denote what a games overall rating is. For example, a game like Super Mario Odyssey, at least going off of its current ratings around the world, would have the Violence descriptor with an exaggerated fictional violence tag (enemies poof out of existence when attacked) and a Distress descriptor with occult characters tag (zombie costume, realistic dinosaurs, etc) within this system. These are then used to decide the ratings through a questionnare. So, if we use Odyssey as our example, it would only have a Violence and Distress descriptor with only one tag each, which would give it an Everyone rating. 

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This brings the best of both worlds in my opinion, as it simplifies the rating system to four ratings and 7 content descriptors that are easy to understand and are universal, and several amounts of tags, which allows for granularity in the content players would like to browse. When combined together, the system could make it easy to know exactly what type of content is in a game. Originally, I had the idea of a level for content ranging from Minimal to Mild to Moderate to Severe for each content descriptor, but after pondering it, that doesn't solve the issue of it being universal, as different cultures have different tolerances for that type of content. Having general and universally understood content descriptors and then more specific tags for specific types of content allow players to easily see the general rating for a game, and to view the descriptor tags for a specific look as to what content is featured, and has the benefit of being searchable within itch.io, being easier to set up in a rating submission form, and is easier to add and edit in the future as it doesn't require developers to consider what severity level their game is and instead be specific as to what the game actually features.

I would really like to see a rating system added to itch.io, and I hope this feedback helps in some way!

I like the idea of doing this but I would expect making things complicated would likely cause problems so from my perspective the following fairly simple solution might work:

Everyone - suitable for all ages.

Shows up in search results.

No content warning regardless of logged on or visiting without logging in.

Example: some sort of flower garden simulator (grow flowers and arrange them in a garden).

Mature - more intense content.

Shows up in search results. 

No content warning if logged in.

Content warning if visiting without logging in.

Example: Some sort of ninja assassin game (sneak around and kill people but not with excessive brutality).

Adult - pretty much anything goes.

The default age rating.

Will not show up in search results unless logged in and a toggle in the profile setting its ticked.

Has a warning if attempting to access it without logging in (like it is already with most of these games).

Has a warning if attempting to access it while logged in and the profile toggle is disabled.

Example: A blatantly obvious porn game (no explanation needed I think).

Where tags are concerned I'm included to leave it to the developer to decide with users that are logged in able to suggest tags however the developer decides if the tag is appropriate or not - specific types of content could be noted here like drug use - to make it easier perhaps a tag cloud of some sort could be made to make tagging accurately easier.

This is a great discussion that needs to happen. Thank you to the Admin and Moderators for leading this effort to improve Itch.io and make it a safe space. I'd like to suggest that perhaps there is a deeper underlying issue underneath. Before coming up with a content/age rating system maybe it would be good to clarify what content is allowed (even within the adult section). I elaborated on this topic on a recent post that suggested a change in the Terms of Service. I encourage you to check it out and take action. Thanks!

Personally I'm more interested in highly specific trigger warnings than in vague age ratings.  For example, a player with extreme arachnophobia might have trouble with games that contain spiders, but be totally fine with sexual content.

Trigger warnings feel genuinely helpful to me.  Age ratings feel condescending.

I also stand against the implementation of a generic age rating system, and would be more happy with some kind of selective "in a category I may dislike" type of warnings system.

And of course there is a huge need for adding some way for users to personally blacklist or ignore games based on tags. At least I can say with confidence, that the "Adult" and "NSFW" section of the site is unpleasant to browse through without any options on content filtering.

My main point is that, people can be adults, with very different tastes in whatever. So a generic "you are 18+ so you are okay with anything" type of system wouldn't work well, and wouldn't improve itch website's current state in any way.

If itch decides to move to a generic, age-based rating system, then at least there should be a separate "For Adults Only" category besides the simple "18+" category, as it's possible to find things on itch with rather odd, uncommon, or extreme content, which surely doesn't pop-up in "simple" "18+" computer games. And here comes in the problem about defining what is allowed in the terms of service and the sensitive matter of artistic freedom and censorship, which I think that anyway can not be enforced without a sophisticated manually supervised curation system, which would at least be able to correctly recognize and tag all games on itch.

By the way, why is it not allowed for users to add tags to games? It would make it a lot more easier to search through the whole selection of games on itch, and more probable to find what people are looking for instead of totally random stuff, even without implementing a tag blacklist system.

so, we are required to add ESRB ratings or something like that???

I don't think this rating is meaningful on the Internet, because games can be downloaded and purchased at will. It can't verify what age people or children bought adult or pornographic content.

If it is a physical CD, the seller can verify the age of the other party (only need to submit the ID card).

In addition, I think that if there is too much adult content, this website will be blocked by many countries because it violates the minor protection law.

The best way is to lock the areas that do not accept porn so that they cannot access pornographic content. Only 16+(or less) content is open to these countries.

That's what STEAM does.

Don't put all your hopes on pornographic content. 

It is not the most profitable thing. 

PAYPAL also prohibits pornographic trading. It would freeze that income.

Maybe I am too old, but frankly, I do not give a  damn for any distinction for  the demographic of the    13-17yo.   You have to be 13yo to use itch per tos. So the only important age restriction is adult yes or no.

Since there is no curator system and no user tags that I would know of,   all games that would have to be   restricted by their content and not by their age appropriateness, would be dependent on the rating of the dev. And those would be    ...   questionable.

For adults that look for games to play with their children, there do be tags.  If it is tagged horror, for kids it ain't. And if the dev of a jump scare game    would not tag horror or similar, that dev surely would not have rated it correctly for any   maturity   preference.

It would be great if we could mute games site wide per tag, so if I don’t want to see any games tagged Adult or Erotic it will hide those results (loooots of NSFW stuff in the Top Sellers list* :P) You can add a button in the list labelled “Some search results are hidden per your muted tags”.

* I mean, good for them, but it’s not something I want to see every time I check out sales trends.

I do not like the idea of age ratings for games (or anything else, for that matter). There's no widespread agreement about "what's appropriate for a 16-year-old but not for a 14-year-old" or even "what's appropriate for 17-year-olds but not 12-year-olds." It's easy to discuss the broad outlines but impossible to find agreement on the edge cases - and labels that don't work on the edge cases are useless.

The most well-known age-based standards are used for movies. But games are not movies, and even if the same standards were attempted ("no more than one, non-sexual use of the F word in a PG-13 movie") (let's not think about what the rating "parental guidance" would mean in video games), it's unclear what that would mean in practice. Does "no more than one" mean "you can absolutely only encounter this once, IF you pick the right path," or can it mean "you can repeat the scene where this happens many times?"

"For adults only" runs into problems as well. Is that:

• Content the creator thinks is appropriate for adults (18+) but not minors (17 or less)?
• Content the creator thinks is illegal for minors? 
• ...in what country?
• Content that contains imagery that would not be shown on daytime TV in the US?
• Content that contains sexual/erotic themes?
• Content that contains extreme violence, gore, or crimes?
• Content that addresses mature, complex story themes?
• ...How do all these rules apply to TTRPGs or text-based games?

Having an official label for "Adult" content, as opposed to a creator-chosen tag, runs the risk of getting legal entanglements. Itch.io might be stuck being responsible for trying to keep minors away from the content - meaning they'd need some kind of age verification attached to the accounts. (Meaning: only honest minors would be blocked from the content. There is no way to do actual age verification online.) 

I'd like better filters and sorting. I'm very fond of AO3's method, but that's not likely applicable in other settings. AO3 has a short list of mandatory tags (including an option to not use any of them), and it relies on a large pool of "tag wrangler" volunteers to make help people find what they want and avoid what they don't. (At the simplest: Tag wrangling would mean making "roguelike" and "rogue-like" both show up in the same search. It cuts down on excess tags.)

I have yet to see a rating system that had objective standards and was applied fairly. (AO3 gets around this with a lot of hand-waving for the edge cases - and by not having any attempt at age verification, just a clickthrough that says "I promise I'm old enough to read this.") I have never seen an age-based system that was willing to answer questions in advance about how a work should be categorized - it's always "put your work up, and if someone complains about it, we may adjust the rating."

I would  much rather there were better tagging & sorting options than an imposed rating system. Even without tag wrangling - give me something like AO3's filters: Let me choose a set of tags to see, a set of tags to avoid, and sort by price or downloads or date updated.