SecurityTrails Alternative: WHOIS, DNS, SSL and Subdomain API

Introduction

SecurityTrails is one of the most recognized names in DNS and domain intelligence. Its strengths are real: current DNS data, historical DNS records, subdomain discovery, IP research, reverse DNS searching, reverse WHOIS/searching workflows, associated domains, and a Domain Specific Language for advanced investigations.

But the pricing starts at $500/month for 20,000 queries. That makes sense for teams that need historical infrastructure pivots every day. It is harder to justify for developers who primarily need current WHOIS, DNS, SSL certificates, domain availability, subdomain discovery, and monitoring inside an application or security pipeline.

This article is an honest comparison of SecurityTrails and WhoisJSON. We do not pretend WhoisJSON replaces every SecurityTrails feature. Instead, we separate the use cases where SecurityTrails is stronger from the workflows where WhoisJSON is simpler, cheaper, and easier to integrate. For a broader provider comparison, see WhoisJSON vs WhoisXML vs Whoxy.

SecurityTrails Alternative: Best Choice by Use Case

The practical question is not "which tool is better?" It is "which tool fits this workflow?" If you need an alternative to SecurityTrails for developers building product features, WhoisJSON is usually the better fit. If you need historical DNS investigation and attribution pivots, SecurityTrails is the stronger platform.

This is also the cleanest way to think about current DNS API vs historical DNS API needs: WhoisJSON focuses on current operational data, while SecurityTrails is built around investigation datasets and historical infrastructure context.

What Is SecurityTrails?

SecurityTrails is a domain and DNS intelligence platform used for asset discovery, threat hunting, attack surface mapping, and infrastructure research. Based on the plan comparison used for this article, its paid plans include current DNS records, historical DNS records, subdomain discovery, domain WHOIS, IP address research, reverse DNS searching, and advanced features such as Domain Specific Language queries and associated domains.

Three capabilities define the SecurityTrails product:

• Historical DNS records: the ability to see how a domain's DNS records changed over time. This is valuable for incident response, threat attribution, and infrastructure reconstruction.
• Reverse searching: reverse DNS and reverse WHOIS/searching workflows help investigators pivot from an IP address, name server, registrant clue, or infrastructure pattern to related domains.
• Advanced investigation language: DSL queries and associated-domain workflows help security teams express complex searches across large datasets.

That focus makes SecurityTrails a serious tool for analysts. It also explains the pricing: it is not positioned as a low-cost developer utility for simple current lookups.

Why Teams Look for a SecurityTrails Alternative

The usual reason is not that SecurityTrails lacks useful data. The usual reason is fit. Many teams do not need historical DNS and reverse-search capabilities often enough to justify a $500/month starting point.

• High starting price: Professional is $500/month for 20,000 queries. Business is $1,500/month for 65,000 queries. Enterprise is custom.
• Current-data workflows are cheaper elsewhere: if your app needs current WHOIS, DNS records, SSL certificates, subdomains, and availability checks, a focused API can be much less expensive.
• No free development tier in the comparison: the provided SecurityTrails plan table starts at Professional. WhoisJSON has a permanent Basic plan with 1,000 requests/month.
• Monitoring is a separate workflow: SecurityTrails is strong for research and search. WhoisJSON includes domain monitoring endpoints and alerts for ongoing change detection.
• SSL certificate inspection is not shown in the provided plan table: WhoisJSON documents a dedicated SSL endpoint for issuer, validity dates, SANs, key size, and fingerprints.

SecurityTrails vs WhoisJSON - Feature Comparison

This table stays deliberately conservative: SecurityTrails features are limited to the plan comparison you provided, while WhoisJSON features are based on the local OpenAPI spec and project pricing.

Pricing Comparison

SecurityTrails is priced for investigation teams and higher-budget security programs. The plan comparison provided for this article lists the following tiers:

WhoisJSON uses self-serve monthly plans. The same API key covers WHOIS, DNS lookup, SSL certificate checks, domain availability, subdomain discovery, and domain monitoring.

What SecurityTrails Does Better

An honest SecurityTrails alternative article has to say this clearly: SecurityTrails is better for historical and investigative search.

• Historical DNS: WhoisJSON does not provide historical DNS records. If you need to reconstruct past infrastructure, SecurityTrails is the stronger choice.
• Reverse DNS and reverse WHOIS/searching: WhoisJSON focuses on direct lookups. SecurityTrails supports reverse-style pivots that are useful for threat hunting.
• DSL queries: advanced search syntax can compress complex analyst workflows into a single query.
• Associated domains: SecurityTrails is built to discover relationships across domains, IPs, and infrastructure clues.
• Consulting and commercial licensing: the plan table includes consulting services and commercial use, which can matter for larger organizations.

Where WhoisJSON Is Stronger

WhoisJSON is stronger when the job is not deep historical investigation, but current domain intelligence inside software.

• Much lower entry price: Basic is free, Pro is $10/month, Ultra is $30/month, and Scale is $50/month for 1,000,000 requests.
• One API key for multiple endpoints: WHOIS/RDAP, DNS, SSL certificate checks, domain availability, subdomain discovery, and monitoring share the same authentication model.
• Documented SSL endpoint: the API returns issuer, validity window, SANs, key size, SHA-1, SHA-256, and SHA-512 fingerprints.
• Monitoring included: teams can create monitors, read monitor history, and receive change alerts instead of only running ad hoc lookups.
• Developer-friendly quota visibility: responses include the `Remaining-Requests` header, so applications can track quota use during a billing period.

API Example: Current Domain Intelligence with WhoisJSON

A SecurityTrails replacement is not always a one-endpoint migration. If your workflow is current-data enrichment, the usual WhoisJSON pattern is to call the specific endpoints you need and combine the result.

import requests

BASE = "https://whoisjson.com/api/v1"
HEADERS = {"Authorization": "TOKEN=YOUR_API_KEY"}

def enrich_domain(domain):
    whois = requests.get(
        f"{BASE}/whois",
        params={"domain": domain},
        headers=HEADERS,
        timeout=15,
    ).json()

    dns = requests.get(
        f"{BASE}/nslookup",
        params={"domain": domain},
        headers=HEADERS,
        timeout=15,
    ).json()

    ssl = requests.get(
        f"{BASE}/ssl-cert-check",
        params={"domain": domain},
        headers=HEADERS,
        timeout=15,
    ).json()

    subdomains = requests.get(
        f"{BASE}/subdomains",
        params={"domain": domain},
        headers=HEADERS,
        timeout=30,
    ).json()

    return {
        "domain": domain,
        "registrar": whois.get("registrar", {}).get("name"),
        "created": whois.get("created"),
        "expires": whois.get("expires"),
        "nameservers": whois.get("nameserver", []),
        "mx": dns.get("MX", []),
        "dmarc": dns.get("DMARC", []),
        "ssl_valid_to": ssl.get("valid_to"),
        "ssl_issuer": ssl.get("issuer", {}),
        "subdomain_count": subdomains.get("total_found"),
    }

print(enrich_domain("example.com"))

Conclusion

SecurityTrails is the right tool when you need historical DNS records, reverse DNS searching, reverse WHOIS/searching, DSL queries, associated domains, and analyst-style infrastructure pivots. Those are real advantages, and WhoisJSON does not claim to replace them.

WhoisJSON is the better fit when you need current WHOIS, DNS, SSL, domain availability, subdomains, and monitoring in a simple developer API. For that workload, the pricing difference is substantial: SecurityTrails starts at $500/month for 20,000 queries, while WhoisJSON starts free and reaches 30,000 requests/month at $10.