Then, whatever project you do, do it for yourself, on your own terms. Make this your space and your time.
If you saw my comic that is based on the Fantasy genre called Mukhtar, you would think I am targeting some specific audience but nope. I made that comic out of passion. I even planning to make another passionate comic in the Sci-fi genre. I never have any target audience, it's for everyone to read and it is up to them whether they liked it or not.
The target audience is ME
Okay but fr I rarely think about target audiences when I write-- I write what I would enjoy reading or find interesting. I guess in that case my target audience ended up being people who find the same or similar things things interesting: psychological horror, darker stories and villains with complicated relationships with the heroes.
For me it way relatively easy I guess, since my stories have pretty clear inspirations in the sense that I can clearly identify 'oh, I want to make something with XYZ vibes'. So my target audience would be the same as the target audience of my inspirations 
One thing though is I don't think it's useful to think of target audience in terms of age/gender etc. Rather, think genres and special interests. If someone posted a panel of your comic onto a subreddit, what community is it most likely to be?
Don't forget you yourself are also part of a demographic. What communities do you frequent? What tropes/inside jokes are they familiar with? You probably have a few insider perspectives already; tap into that!
I'm kind of bad at aiming for a specific sort of audience. There are a few things I've been trying recently to really narrow things down because I would like to pitch some stuff at some point, and I also of course work for a company that makes edutainment for kids, so I've had to learn to deliberately write for different age groups.
Look up research on what different audiences react to. One of the things we get at work are all these research presentations and things about what colours age groups react to, how they play, how and when they read and watch, how they identify with characters, how many things they're a fan of, their vocabulary level etc. Actually a really good resource when writing for kids is to look up the school curriculum or syllabus for that age group to find out what the base level expectation of knowledge and vocabulary is for them.
Comp titles. A comp title (comparison title) is a series you can point to and say "it's kinda like this" when pitching to publishers. A comp title should be in the same medium and aimed at the same audience as the thing you want to make (so a mistake I made on Errant was I went in with Netflix She-Ra and Steven Universe as comp titles even though they're animated and webcomics are a different medium with different demographics and trends), they need to be within the last 10 years, and they need to have done pretty well (A publisher isn't going to be put at ease if you say "it's like this comic that was a total flop."). So if I wanted to pitch Errant as a Tapas Original now, I'd have Pandora's Devils and Hard Lacquer as my comp titles (because most people who subscribe to Errant have them in their libraries and they're both popular Tapas Originals), and for a print comic I'm planning that's for kids, I have things like Witch Boy and Amulet: The Stonekeeper. A good start is asking friends for recommendations, seeing what people who follow your work are into and just reading a bunch of comics and being like "Aha! This one is my vibe!"
25 days later
Like @smokesalty wrote,
my target audience is usually me.
But that depends on what I want to achieve, I´m taking part in a comic contest right now,
the comic will be printed when we win and be eventually read by kids, that means the target
audience can´t be me anymore and I will make it kid friendly
My target audience is pretty niche. (Anyone who likes sci-fi horror with industrial themes, body horror, etc. and also like manga art.) I didn't really have a set plan but I just post my work and follow similar creators. It's helped build an audience over the years. 
My target demographic would be older teens and young adults who are into Pastel Goth, dark and edgy stuff. My series "Stacy The Demon Killer" is a parody and mix between Buffy the vampire slayer and devil may cry. It gets pretty violent with all the blood,gore, and swearing, so it's definitely not for everyone.
My two series is targeted towards battle shonen and seinan fans, though they're both novels. One I made Crusaded Defender is a series that I hoped HxH Fans would like and Agents of Salvation is a series that I believe would gain the attention of D.gray-man/monster fans so these are not flat out plagiarized carbon copies, there's just inspiration from those series mixed in. I also was targeting an audience who was in late teens/early adults range, both series are action, with Agents being horror and tragedy, and CD being Adventure. In the end I hope that kind of audience is present on this platform.
I honestly don't decide on that, nor even think about it too much.
I'm an artist for hire, so, for the three webcomics that I work for I just apply for the job if the story interests me and the pay is something I can consider a win.
When it comes to my personal projects, I don't have great dreams of making my work noticeable, to be popular or to expect it to be animated in any kind of format. I never thought about that because I have no one else to satisfy besides myself
I'm very simple, I just think: "I want to do something in a certain way because I don't find content like this or that is specific in X aspect / I had this idea stuck in my head and began to make a story around it"
18 days later
Mine is somewhere between 12 (British equivalent of pg-13) and 15 rated, due to the fantasy violence, disturbing topics and occasional gore. I didn't want it to be too childish, but I didn't want to write a hardcore adult story, so I settled on a teen and up audience.
short answer I dont decide the audience, since im writing this story for myself first and formost that came second.
i have however noticed most of the people who read it or the people i show it to and like it a lot are people who identify deeply with what the story is telling readership seems to be 50/50 boys and girls and mostly in their mid- late 20s
A lot of other people tell me the story makes them uncomfortable cause of the subject matter or its good but its not for them.
There are folks who share similar interests to you and your story may resonate with them.
However, some niches or groups may be found more easily on different parts like other websites.
If you can identify your potential audience it's a great idea to write it down. Just a warning......writing "everyone" doesn't count 
24 days later
in general i am targeting 13 and up , those into scifi fanatsy the furry aspect is also another part as you dont see to many super anthros that dont invole alot sex
24 days later
My target audience.. I only think about these things in vague terms, so apologies if this won't be that helpful.
I'm thinking 15+, definitely not for small children but not adults only, low fantasy fans who like the manga artstyle.
Hm I actually decided mine would be for young adults and up, after careful consideration of the themes. However, since my story is a fancomic, it will pull in younger people that recognize the show which creates some conflict since they're probably going to run into really dark themes that they might not be looking for. Expecting it to be cute all the way, so, the only thing I can do is warn them about it xD
But you know, it's really hard to control who reads your stuff, since for example... My art style is on the 'cute' side so it will attract younger people since the art style is already selling it to that audience, so, the best thing I can do is introduce the 'dark' elements little by little to deter those expecting something different (like only comedy and romance) and get the people that feel interested on the more mature subjects stay.
The fandom around my fancomic's show love shipping characters and romance, so I had to make a great effort to make the point early on that the story wasn't about that at all.
As for the reason I made this comic (it might help you think things through that's why I mention it), it's because in this show (The powerpuff girls) I was unsatisfied by how little the rowdyruff boys appeared, I also wanted to base the story around one of the episodes in which Mojo and Him are fighting over who is the most evil father and I wanted to write something psychological, as I was interested in fleshing out their personalities and inner worlds.
All of this out of the dissatisfaction from not seeing enough of them. However, I knew my story was going to be mature and people seeking romance weren't going to care for it, thus, I remember the first thing I did was to scare them from the beginning as some sort of filter xD
But anyway, you see, you have to first know what you really want to talk about in your story, the ideas in your story are what dictates your audience after all. Just like in the case I described above, if you're talking about mature subjects that won't be appreciated by younger audiences or you know younger people will have a hard time, then you have to consider targeting an older audience.
So in my case, I would suggest you to consider if the themes in your story are relevant to children, teens, adults.
One might want to market it to everyone possible but in the long run, you'll feel limited, since you can't show the same things to children than teens for example. Think well what you feel passionate talking about in your story and think well which audience would appreciate it the best.
I think that's the best I could say about this, hope I helped somehow!
25 days later
umping this thread as well.