I am using the free tier, but I want to prevent going beyond that and being charged.
How do I do this?
Hello! We don’t have any way to limit billing to $0. With the exception of bandwidth, you only pay for what you manually provision. So anything paid is intentional. This isn’t a pay-per-request product where 10 million people show up and you get a big bill at the end.
We do have prepaid support. You can buy $25 or more of credits and we suspend the account when credits are exhausted.
For what it’s worth, we probably won’t build a way to prevent accounts from using paid services. We pay the cost to run free services with the hope that people will deploy projects that are worth paying for when we’ve proven that what we’re doing is valuable.
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In lieu of billing limits, is there a place to see what their estimated monthly spending will be?
It’s pretty opaque from both flyctl as well as from the fly.io dashboard how much your resources should generally cost per month.
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@kurt Some of the items are billed on a “per request” basis (bandwidth) which is what I am concerned about.
I like Fly and would pay for it in the future, but at the moment I have a demo app that I do not want racking up large bills without me knowing.
I think I may use the credits, thanks for the reply.
You can see “usage so far this month” here: https://fly.io/organizations/personal
Stripe doesn’t give us much better data than that, and all our billing is “fire off metrics to stripe, let them generate invoices”. We’ll have to build a new billing system sometime in the next year and I think it’ll improve then.
Ah, yes this is a fair point. Bandwidth is incredibly cheap on Fly, but it costs us money when you use it. We’ve debated ways of making it “safe” to handle unintentional bursts, but so far it hasn’t hit anyone. People pay us for VM time long before bandwidth surpasses the limit. We give away a lot. 
Hi Kurt, I was wondering if I could ask about this.
I completely understand your point about Fly having to pay for free users’ bandwidth. But just to be clear, are you saying that my current free app could rack up a bill, if say someone on the internet found my app and started refreshing it over and over, using lots of bandwidth?
Perhaps that’s not a realistic scenario, especially since you give a 100GB free allowance for North American + European traffic. But it’s possible, from what you’re saying? And even though I don’t have any payment methods attached to my account right now, I would still be legally liable for that bill? Although I don’t live in the US so I don’t know how that legally works.
Like I say, I completely understand your point about Fly having to cover the costs even of free users, that makes complete sense. I just wanted to be clear about how your billing works.
Thanks if you’ve read my post, I appreciate it.