Findomain Alternative — Free Online Subdomain Finder
Findomain is one of the fastest subdomain finders in the open-source ecosystem — a Rust binary that enumerates passive sources at speeds Go and Python tools struggle to match, with built-in monitoring, HTTP probing, and screenshot capture. It is also something you have to download, configure, and keep updated. SubDomainsFinder.com covers the same passive recon ground from any browser, adds IP, port, and ASN data per subdomain, and asks nothing of your local machine.
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TL;DR — when to use which
- Use SubDomainsFinder when you need a fast, browser-based subdomain scan with IP, port, and ASN context — no install, no flags, no API tokens.
- Use Findomain when you need raw enumeration speed against large target lists, continuous monitoring with webhook alerts, or structured output to JSON, MySQL, PostgreSQL, or SQLite.
- Use both for lightweight browser triage alongside a persistent Findomain monitoring instance on the same targets.
What is Findomain?
Findomain is an open-source subdomain enumeration tool written in Rust, hosted at github.com/Findomain/Findomain. Its core proposition is speed: by compiling to a single statically linked native binary, it avoids the runtime overhead that Go and Python tools incur. Sources include Certificate Transparency logs via crt.sh, the Sublist3r historical database, Anubis, VirusTotal, and a long list of OSINT endpoints. Some sources, notably paid providers like Spyse, require API tokens configured via environment variables.
Beyond enumeration, Findomain bundles features that other tools delegate to their ecosystem: --resolved for DNS resolution, --http-status for inline HTTP probing, a basic port scanner, and Chromium-driven screenshot capture. Output formats include stdout, flat files, JSON, MySQL, PostgreSQL, and SQLite. The standout feature is monitoring: run with the monitoring flag, Findomain watches a target continuously and pushes Slack/Discord/Telegram alerts when new subdomains appear.
# Linux (latest binary)
curl -LO https://github.com/Findomain/Findomain/releases/latest/download/findomain-linux
chmod +x findomain-linux
./findomain-linux -t example.com
# macOS via Homebrew
brew install findomain
# Resolve + HTTP status check
findomain -t example.com --resolved --http-status
# JSON output
findomain -t example.com -o results.jsonFeature comparison
| Feature | SubDomainsFinder | Findomain |
|---|---|---|
| No installation required | ||
| Browser-based UI | ||
| Passive subdomain discovery | ||
| Continuous monitoring with alerts | ||
| HTTP status check built-in | ||
| Open ports detectionFindomain has a basic port scanner | ||
| ASN & hosting provider | ||
| Screenshot capture | ||
| JSON / SQL output formats | ||
| Free to useFindomain monitoring is paid SaaS | ||
| Open source | ||
| Actively maintained |
Yes No Partial / limited
Where Findomain excels
- Raw speed. Rust's zero-cost abstractions give Findomain a real performance edge on large workloads. On thousands of targets the wall-clock difference against Go or Python equivalents is noticeable.
- Continuous monitoring with alerts. Configure a SQL backend, set up a webhook, drop Findomain into a cron job, and you have a fully functional new-subdomain alerter — free if self-hosted.
- Integrated HTTP and port checking. With
--resolved,--http-status, and the built-in port scanner, you get usable triage from a single command without chaining httpx and naabu. - Database output formats. MySQL, PostgreSQL, and SQLite output removes an ETL step for teams building an asset inventory database.
- Single statically linked binary. No runtime dependency, no Python version mismatch. Copy the binary to any server and it runs.
Where SubDomainsFinder has the edge
- No download, no install. Findomain is a single binary, but on a borrowed laptop, a locked-down workstation, or an iPad, SubDomainsFinder is the only option of the two that actually works.
- Instant results without a flag curve. Findomain has dozens of options. SubDomainsFinder asks for a domain and shows results — the investment to a first useful answer is seconds.
- Port, ASN, and CDN data per subdomain. Findomain's built-in port scanner is basic and ASN data is not part of its output. SubDomainsFinder returns resolved IPs, open ports, ASN, and hosting provider in one view by default.
- No API token management. Findomain's most expansive coverage involves paid OSINT providers and the keys to query them. SubDomainsFinder aggregates from CT logs and public scan data without any of that overhead.
- Usable by non-technical stakeholders. A security manager, product owner, or journalist who needs to understand a domain's footprint can use SubDomainsFinder without a terminal.
Which tool is right for you?
Pentesters & bug bounty
Use SubDomainsFinder for fast initial triage with IP and port context. Run Findomain in monitoring mode against in-scope targets so you catch newly-provisioned subdomains automatically. The combination of a quick browser scanner and a persistent monitor is hard to beat for free.
Blue teams & defenders
SubDomainsFinder handles spot checks and onboarding new domains. For continuous attack surface monitoring with alerts on new subdomains, Findomain with a SQL backend and a Slack webhook is the natural operational choice — it runs unattended and stores history.
Sysadmins & IT teams
If you need to know what subdomains exist for a domain you manage, SubDomainsFinder answers that instantly with no install. Findomain becomes worth the setup only when you want ongoing monitoring or need to feed results into a database.
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