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Lightweight open source reCaptcha alternative
- rahimnathwani 1y agoIs there a live demo anywhere? I didn't see one linked in the README or on the official site's home page.
- unixfox 1y agoYes found one: https://altcha.org/captcha/ https://altcha.org/captcha/
- immibis 1y agoThe purpose of reCaptcha is to enhance your Google user profile and to deny legitimate users. How does this alternative accomplish those things? This appears to be a proof-of-work, like Anubis. Real captchas collect much more fingerprinting data to ensure that only users with the latest version of Chrome, the latest version of Windows, and an Nvidia graphics card, can use the site.
- literalAardvark 1y agoYeah, this fails at its most important task, making those filthy, dirty, Firefox users click on bridges for 1 hour a day. On topic though, how does this improve on hCaptcha?
- akimbostrawman 1y agoDon't forget those criminals with non-residential IPs
- Semaphor 1y ago> On topic though, how does this improve on hCaptcha? Cloud vs self-hosted, click annoying things challenge vs automatic proof of work. Or are there other hCaptcha versions and I just never realized it?
- Imustaskforhelp 1y agooh yes. as a firefox (now librewolf) user, it deeply saddens me.
- g-b-r 1y agoI know some people who quickly give up and renounce using the service, when they run into hCaptcha puzzles. I've been bewildered for some time as well, honestly, it took me a while to figure out the first I ran into. And trying one now, fully knowing that I'd have to solve one, I was dumbfounded by the puzzle I've gotten, it took me a few seconds to understand it. Cloudflare's ones are horrible and a plague (although they might have slightly improved recently), but I'm not certain I'd prefer hCaptchas over them.
- Semaphor 1y agoI know this is partially a joke, but I’d like to mention that as a Firefox user with uBo and uMatrix, I almost never have to solve challenges with ReCaptcha.
- hexagonwin 1y agohow? do you just allow all cookies/scripts/xhr on your umatrix? i'm on a similar config and I get captchas far often than any other users on the same network for some reason.
- Semaphor 1y agoI use the uMatrix plugin to automatically allow what’s required for ReCaptcha, that tends to work. I do get the annoying picker sometimes and have an AI extension to solve it for me, but it’s relatively rare, like 1 out of 5 times max (I generally don’t see RC that often). No idea how I’d compare to others on my Network, that’d only be my wife and as a Linux user she’d probably get more than me with Windows ;)
- pabs3 1y agoI thought uMatrix got abandoned?
- serhack_ 1y agoThe real secret of an effective captcha-like system is to identify/collect lots of data, identify suspicious patterns, validate them (checking what kind of data exposes a bot-like system) and then use this for serving dynamic challenges based on a couple of information. Example: if the system identifies the user as a bot, it tries to give a less performant solution in terms of PoW.
- Imustaskforhelp 1y agoMaybe somebody could explain me why your comment is in different contrast of grey? I think somebody might have flagged your comment, but it is a real fact. This is one of the reasons why people say cloudflare owns the majority of internet but I think I am okay with that since cloudflare is pretty chill. And they provide the best services but still it just shows that the internet isn't that decentralized. But google captcha is literally tracking you IIRC, I would personally prefer hcaptcha if you want centralized solution or anubis if you want to self host (I Prefer anubis I guess)
- ArinaS 1y agoCloudflare is not chill because they, either ignorantly or purposefully, block everything that's not Chromium or Firefox[1]. Or sometimes everything that's not just Chromium[2]. [1] - https://www.theregister.com/2025/03/04/cloudflare_blocking_niche_browsers/ https://www.theregister.com/2025/03/04/cloudflare_blocking_n... [2] - https://www.techradar.com/pro/cloudflare-admits-security-tool-is-blocking-some-challenger-browsers https://www.techradar.com/pro/cloudflare-admits-security-too...
- ronsor 1y agoDon't worry. They sometimes block Chromium too.
- Zak 1y ago> Maybe somebody could explain me why your comment is in different contrast of grey? Downvotes. Comments with negative scores are shown with lower contrast. The more negative the score, the less contrast they get.
- Jleagle 1y agoCan someone explain why a robot would not be able to calculate the PoW?
- jsheard 1y agoIt could, the idea is just to tip the economics such that it's not worth it for the bot operator. That kind of abuse typically happens at a vast scale where the cost of solving the challenges adds up fast.
- hombre_fatal 1y agoBotnets don't even use their own hardware. Why would someone renting dirt cheap botnet time care if the requests take a few seconds longer to your site? Plus, the requests are still getting through after waiting a few seconds, so it does nothing for the website operator and just burns battery for legit users.
- jsheard 1y agoBotnets just shift the bottleneck from "how much compute can they afford to buy legit" to "how many machines can they compromise or afford to buy on the black market". Either way it's a finite resource, so making each abusive request >10,000x more expensive still severely limits how much damage they can do, especially when a lot of botnet nodes are IoT junk with barely any CPU power to speak of.
- victorbjorklund 1y agoThere is still an opportunity cost. They can scrape just your site or they can scrape 100 other sites without POW (no idea if it is 10, 100 etc)
- Jleagle 1y agoSo it's the same as a sleep()
- progx 1y agoIn AI century, how you would detect a real person or an AI?
- ArinaS 1y agoThis thing, despite using "captcha" in its name, is not your typical captcha like hCaptcha or Google's one, because it uses a proof-of-work mechanism instead of writing answers in textboxes/clicking on images/other means of verification requiring user input. AI bots can't solve proof-of-work challenges because browsers they use for scraping don't support features needed to solve them. This is highlighted by existence of other proof-of-work solutions designed to specifically filter out AI bots, like go-away[1] or Anubis[2]. And yes, they work - once GNOME deployed one of these proof-of-work challenges on their gitlab instance, traffic on it fell by 97%[3]. [1] - https://git.gammaspectra.live/git/go-away https://git.gammaspectra.live/git/go-away [2] - https://github.com/TecharoHQ/anubis https://github.com/TecharoHQ/anubis [3] - https://thelibre.news/foss-infrastructure-is-under-attack-by-ai-companies/ https://thelibre.news/foss-infrastructure-is-under-attack-by...: "According to Bart Piotrowski, in around two hours and a half they received 81k total requests, and out of those only 3% passed Anubi's proof of work, hinting at 97% of the traffic being bots."
- graemep 1y ago> AI bots can't solve proof-of-work challenges because browsers they use for scraping don't support features needed to solve them. At least sometimes. I do not know about AI scraping but there are plenty of scraping solutions that do run JS. It also puts of some genuine users like me who prefer to keep JS off. The 97% is only accurate if you assume a zero false positive rate.
- ArinaS 1y ago> "It also puts of some genuine users like me who prefer to keep JS off." Non-javascript challenges are also available[1]. > "The 97% is only accurate if you assume a zero false positive rate." GNOME's gitlab instance is not something people visit daily like Wikipedia, so it's a negligible amount of false positives. [1] - https://git.gammaspectra.live/git/go-away/wiki/Challenges#non-javascript https://git.gammaspectra.live/git/go-away/wiki/Challenges#no...
- chrismorgan 1y agoCAPTCHA stood for “Completely Automated Public Turing Test to tell Computers and Humans Apart”. By this point, it’s obvious that that has failed, and even that no general solution is possible any more. ALTCHA… telling Computers and Humans Apart? No, this is proof of work, meaning it’s just about making things expensive—abuse control, not actually distinguishing between computers and humans. In fact, in https://altcha.org/captcha/ https://altcha.org/captcha/ one of the headings is Inclusive to Robots! This is so far the opposite of traditional CAPTCHA, on the technical side, that it’s mildly hilarious. (Socially, they largely amount to the same thing—people never did actually care about computers, just abusive bots.) Then the question is: what is the proof of work mechanism? How robust are things going to be, and can you ensure attacking will remain expensive, without burdening users too much? https://altcha.org/docs/proof-of-work/ https://altcha.org/docs/proof-of-work/ indicates it’s SHA hashing, not something like scrypt. Uh oh. The best specialised hardware is several million times as good as good laptops¹, let alone cheap phones. If this were to become popular, bots would switch to such hardware, probably making the cost of attacking practically negligible. https://altcha.org/docs/complexity/ https://altcha.org/docs/complexity/ shows they’ve thought about these things, but I feel that although it will work for a while, it’s ultimately a doomed game. And in the mean time, you can normally go waaaay simpler and less intrusive: most bots are extremely dumb. Is “captcha” heading in the direction of meaning “bad rate limiting”? Because really that’s what this stuff is: rate limiting that trusts that clients don’t have lots of compute power conveniently available, but will get vaporised by powerful and intentional adversaries. —⁂— ¹ On the https://altcha.org/docs/complexity/ https://altcha.org/docs/complexity/ test, a comparatively ideal browser on my 5800HS laptop might reach 500,000 SHA-256 hashes per second at a cost of at least 25W. (Chromium gets half this with ~50% CPU usage; Firefox one tenth, altogether failing to load the cores for some reason.) The most energy-efficient commercial Bitcoin miners seem to be doing around 80 billion of these hashes per watt-second. That’s four million times as good. You cannot bridge such a divide.
- immibis 1y agoWelcome to the post-competence era. Words don't mean things. https://news.ycombinator.com/context?id=43998547 https://news.ycombinator.com/context?id=43998547
- binary132 1y agoIt’s crazy how much of the internet and our app stacks depend on proprietary hosted service integrations that will almost certainly disappear or break in time. Sure it’s convenient to get off the ground with but it doesn’t make sense to me to gate your functionality on a third party that can easily break or slip out from under you. It would be one thing if proprietary software was distributed in a form you could keep operating and using on your own, but even that is obviously inferior to being able to “repair your own equipment”.
- IgorPartola 1y agoreCaptcha is routinely broken for me. Almost every time I see it I have to solve it about a dozen times, then it decides I’m not human. After 2-3 page refreshes it does let up but it’s frustrating as hell.
- wkat4242 1y agoAre you on Linux by any chance? For some reason this is now deemed 'suspicious' by recaptcha and cloudflare :( Especially if you use Firefox. It's driving me crazy getting bombarded by these.
- worldsavior 1y agoDid you try faking user agent?
- wkat4242 1y agoYes but that made it worse. In fact I used to fake user agent all the time because Microsoft 365 is so retarded. With the Firefox/Linux user agent a lot of features don't work. When it pretends to be MS Edge it works fine. Clearly trying to force people to use the 'invented here' browser :( But as I was getting captcha's I moved to using it only for the MS365 sites and nowhere else. It seems to have reduced the captcha's somewhat, especially the ones that never end (keep looping). But I still get a ton of "Your browser is suspicious, here's an extra check" nonsense from Cloudflare in particular.
- pabs3 1y agoHmm, how do they know you have calculated the PoW without setting a cookie? Or do you have to calculate it on every page load?
- jrochkind1 1y agoyeah, I need more info to understand what's up. Maybe it's only used on individual form submit (like the classic captcha use-case), and not on a page load, and it does have to be recalculated on every form submit?
- alamsterdam 1y agoYes, I was wondering what is to stop you replaying the same PoW multiple times. All I can find is: To prevent the vulnerability of “replay attacks,” where a client resubmits the same solution multiple times, the server should implement measures that invalidate previously solved challenges. The server should maintain a registry of solved challenges and reject any submissions that attempt to reuse a challenge that has already been successfully solved. This doesn't seem very scaleable? Or am I missing something?
- dankobgd 1y agorecaptcha is useless, only annoys actual users. I lost 15 minutes last week on miui site with their trash recaptcha. The point is to steal more data from you
- remram 1y agoWhy call it a CAPTCHA if it is not even trying to tell Computers and Humans Apart (CHA)? This is only trying to tell human browsers from bot browsers apart. Not even that, it seems all it does is slow all browsers down equally.
- immibis 1y agoBecause <s>human</s> western society is in its post-competence era. It doesn't matter whether you can do your job, only whether your manager thinks you are, and they don't understand your job so they use all the wrong metrics. Like whether there's a checkbox you have to click, and whether it spins for a while when you click it. That's a CAPTCHA now. And working is when your butt is in the chair. And investing is when you give someone money and they promise to give more back tater. And food is things that fit in your mouth and don't kill you. And free speech is when you get turned away at the border for disliking the president on social media. And top-of-the-line CPUs are ones that die within 24 months. Meanwhile the totalitarian dictatorship across the pond actually does all these things better somehow (except the politics). https://en.wikipedia.org/wiki/HyperNormalisation#Etymology https://en.wikipedia.org/wiki/HyperNormalisation#Etymology