[ 01 ]What it looks like
A checkbox-style widget that ticks itself in about a second, with no challenge shown.
Captcha type · ALTCHA (open source)
ALTCHA solver API
ALTCHA proof-of-work widgets solved into a valid payload token. A newer self-hosted challenge type that most solving services do not price at all.
Also searched asaltcha bypassaltcha proof of workaltcha widget tokenself-hosted captcha solveraltcha sentinel
- Price
- $4.49
- per 1,000
- Token acceptance
- 99.8%
- Median solve
- 2.6s
- p95 solve
- 5.7s
[ 02 ]Why it is hard
The hash-based proof of work is the cheapest computation on this list. The difficulty is retrieval: the challenge arrives either as a challenge_url the widget fetches or as raw challenge JSON already inlined in the page, and you send one or the other, never both. Self-hosted deployments run on the customer's own domain with their own difficulty setting, so there is no single endpoint to target.
[ 03 ]How we solve it
Post the page URL with either challengeUrl or challengeJson and we return the base64 payload the widget would have produced. Difficulty is read from the challenge itself, so an instance tuned high costs a little more latency and the same price per solve. A malformed or expired challenge comes back as an error rather than a wrong answer, and is not billed.
[ 02 ]Solve it in five lines
Solve it in five lines
Post the task, get the token. Our SDKs collapse creation, polling and retries into one call.
altcha.sh
curl -s https://api.nexcaptcha.net/createTask \
-H "Content-Type: application/json" \
-d '{
"clientKey": "YOUR_API_KEY",
"task": {
"type": "AltchaTaskProxyless",
"websiteURL": "...",
"challengeUrl": "..."
}
}'Required parameters
- API task type
- AltchaTaskProxyless
- websiteURL
- required
- challengeUrl
- required
- Difficulty
- Easy
[ 05 ]Questions about this one
Questions about this one
$4.49 per 1,000 successful solves. It is priced above Friendly Captcha because self-hosted instances set their own difficulty and the worst case is much heavier than the median.
Whichever the page actually gives you, and only one of them. If the widget has a challenge_url attribute, send that; if the challenge object is already inlined in the HTML, send the JSON and skip the fetch, which is usually a second faster.
No. ALTCHA verification is a hash check against the challenge, not against your IP, so the proxyless task is the normal path for both the hosted and self-hosted forms.
Yes. Self-hosted instances are the common case here. Send the challenge as the page serves it and the solve is computed at whatever difficulty that instance sets, at the same price.
Solve your first thousand on us.
Create a key, paste it into the sample above, and watch a real token come back. No card, no sales call.