Domain, WHOIS, IP and DNS data APIs and research tools.
Best for: Developers and analysts needing WHOIS and DNS data programmatically.
Top-rated in Domain ResearchDomains & DNS
From $30/mo (varies by queries)Free plan
Domain Research Tools
Check a domain's availability, history, and ownership before you buy it or build on it.
Best Domain Research Tools
Domain research can mean several things: checking present registration data, looking back at ownership changes, reviewing DNS and hosting history, finding related domains, or screening expired names before acquisition. The strongest tool depends on whether the job is investigative, technical, or investment-oriented. Historical WHOIS and DNS coverage, reverse lookups, monitoring, backlink metrics, and access through an API are the main dividing lines.
By SEM Solutions Editorial Team. Researched from vendor documentation, not hands-on testing. Ordered by Overall Score. Checked October 7, 2026. How we research
API-first domain data
WhoisXML API
Overall Score57/1003.8Editor RatingMarket Signal 43#1 of 5 in Domain Research
WhoisXML API is designed around programmatic access to domain, WHOIS, DNS, IP, and related intelligence. Teams can use APIs and data feeds for registration lookups, monitoring, reverse searches, and infrastructure analysis, so domains do not have to be researched manually one at a time.
- WHOIS API
- DNS data
- Domain monitoring
- IP intelligence
- Best for
- Developers and data teams that need domain research inside applications or automated workflows.
- Consider
- API-based research requires the team to build its own interface, filtering, or downstream analysis around the returned data.
For expired-domain screening
ExpiredDomains.net
Overall Score54/1003.7Editor RatingMarket Signal 41#2 of 5 in Domain Research
ExpiredDomains.net organizes deleted, expiring, auction, and marketplace domains into searchable lists with filtering, watchlists, and saved searches. This serves acquisition research where the main task is narrowing large domain lists before doing deeper history or backlink checks elsewhere.
- Deleted-domain lists
- Marketplace lists
- Filters
- Saved searches
- Best for
- Domain investors and SEO teams screening large numbers of expiring or deleted names.
- Consider
- It is a discovery and filtering environment instead of a full historical ownership or DNS-intelligence platform.
For ownership and history
DomainTools
Overall Score43/1002.2Editor RatingMarket Signal 55#3 of 5 in Domain Research
DomainTools provides current and historical domain-registration research through WHOIS, WHOIS History, Domain History, reverse lookups, monitoring, and Iris tools. Its history data can show changes in registration, DNS, web content, screenshots, and certificates, making it useful for deeper investigations beyond a simple lookup.
- WHOIS History
- Domain History
- Reverse lookups
- Monitoring
- Best for
- Researchers and security teams that need historical ownership and infrastructure context.
- Consider
- WHOIS availability has changed as registries move toward RDAP, so current public registration data can be more limited than older historical records.
Historical DNS research
SecurityTrails
Overall Score42/1003.2Editor RatingMarket Signal 31#4 of 5 in Domain Research
SecurityTrails covers DNS and infrastructure history, including historical records, IP relationships, domain information, and API access. Consider it when the research question is how a domain's infrastructure changed or which domains share related DNS or IP attributes.
- Historical DNS
- IP intelligence
- Domain data
- REST API
- Best for
- Security, infrastructure, and research teams investigating domain and DNS relationships.
- Consider
- It is more infrastructure-focused than a domain marketplace or expired-domain buying tool.
Metric-driven domain research
DomCop
Overall Score34/1002.6Editor RatingMarket Signal 29#5 of 5 in Domain Research
DomCop aggregates expiring and expired-domain lists and layers SEO metrics from sources such as Majestic, Moz, Ahrefs, and Semrush over them. That helps buyers filter by authority and backlink-related signals before manually checking history and relevance.
- Expired-domain lists
- SEO metric filters
- Auction discovery
- Saved searches
- Best for
- Domain buyers who want SEO metrics built directly into expired-domain screening.
- Consider
- Third-party metrics are useful filters but do not replace manual history, trademark, or backlink-quality review.
How to choose
- Work out whether you need current registration, historical ownership, DNS history, or acquisition screening.
- Use historical data when a domain's past use matters.
- Expired-domain buyers should combine metrics with manual history checks.
- APIs matter when domain research needs to run at scale.
All Domain Research Tools (5)
Ranked by Overall Score: our Editor Rating and Market Signal, 50/50. Market Signal uses Ahrefs and Semrush data through September 2026, pulled October 6, 2026. How we score
Daily lists of expiring and deleted domains.
Best for: SEOs and domain investors hunting expired domains.
Domains & DNS
FreeFree plan
Domain and DNS intelligence, including WHOIS history.
Best for: Security and research teams investigating domains and their ownership history.
Domains & DNS
Historical DNS and WHOIS data via API.
Best for: Researchers needing historical DNS and WHOIS records.
Domains & DNS
From $500/mo
Expired domain finder with Ahrefs, Moz and Majestic metrics.
Best for: SEOs evaluating expired domains by backlink profile.
Domains & DNS
From $98/mo
Frequently Asked Questions
Why check domain history before buying?⌄
A domain may have changed owners, hosting, content, or purpose. Historical WHOIS, DNS, screenshots, and backlink data can expose issues that are not visible from the current site.
Is WHOIS still enough for ownership research?⌄
Not always. Privacy rules and the transition toward RDAP mean current registration details can be limited, so historical and infrastructure data may be needed for a fuller picture.
Do any of the tools listed under Domain Research have a free plan?⌄
Yes, WhoisXML API and ExpiredDomains.net both offer a free plan. Free tiers usually come with usage limits, so check whether they cover your volume before relying on them long-term.
Which tool listed under Domain Research has the lowest starting price?⌄
Among the tools listed here whose main product is in this category and whose pricing we've verified, WhoisXML API has the lowest listed starting price: $30/mo (varies by queries). Starting price isn't the whole picture, so check what's included at that tier before deciding.