# crt.guru vs s3viewer: side-by-side comparison (2026)

[crt.guru](https://cybersectools.com/tools/crtguru) is a commercial [external attack surface management](https://cybersectools.com/categories/external-asm) solution by [Crt.guru](https://cybersectools.com/companies/crtguru). [s3viewer](https://cybersectools.com/tools/s3viewer) is a free [external attack surface management](https://cybersectools.com/categories/external-asm) solution. Features, integrations, deployment and the company behind each one, side by side.

Need the answer fast? [Best Attack Surface Management Solutions for Business](https://cybersectools.com/shortlists/best-attack-surface-solutions) picks Palo Alto Networks Cortex Xpanse, Microsoft Defender EASM, Mandiant Attack Surface Management and 4 more.

## Side-by-side comparison

| | crt.guru | s3viewer |
|---|---|---|
| Pricing model | Commercial | Free |
| Category | External Attack Surface Management | External Attack Surface Management |
| Verified | No | No |
| Deployment type | Cloud | Cloud |
| Company size fit | Startup, SMB, Mid-Market, Enterprise | SMB, Mid-Market, Enterprise |
| GitHub stars | – | 448 |
| Last commit | – | Jul 2023 |
| Company | Crt.guru | – |
| Headquarters | – | – |

### Use cases and capabilities

| | crt.guru | s3viewer |
|---|---|---|
| TLS | Yes | – |
| SSL | Yes | – |
| PCI DSS | Yes | – |
| NIST | Yes | – |
| Security Scanning | Yes | – |
| Alerting | Yes | – |
| Security Compliance Training | Yes | – |
| Security Reporting | Yes | – |
| Vulnerability | Yes | – |
| REST API | Yes | – |
| Azure | – | Yes |
| S3 | – | Yes |
| AWS | – | Yes |
| Misconfiguration | – | Yes |

### Core features

**crt.guru**

10 features listed. Sign in on the page to see them.

**s3viewer**

No features listed.

### Integrations

**crt.guru**

4 integrations listed. Sign in on the page to see them.

**s3viewer**

No integrations listed.

## Which one fits you

Based on what each listing shows: deployment, company size, price and open source.

- [crt.guru](https://cybersectools.com/tools/crtguru) fits if you are a startup.
- [s3viewer](https://cybersectools.com/tools/s3viewer) fits if you need a free product and you want an open-source product.

## crt.guru vs s3viewer FAQ

Common questions when comparing crt.guru vs s3viewer for external attack surface management.

### What is the difference between crt.guru and s3viewer?

**crt.guru**: External TLS cert monitoring with expiry alerts, vuln scanning & compliance reports. Built by Crt.guru.

**s3viewer**: A storage exploration tool that provides unified access to view publicly accessible Amazon S3 buckets, Azure Blob storage, FTP servers, and HTTP directory listings.

The table above shows where their features, integrations, deployment and company size fit differ.

### Who makes crt.guru and s3viewer?

**crt.guru** is made by Crt.guru. **s3viewer** is open-source with 448 GitHub stars. The vendor behind a product decides its roadmap, support, and longevity, so check each company's profile before you commit.

### Is crt.guru a good alternative to s3viewer?

Often, yes. crt.guru and s3viewer are both External Attack Surface Management products. Key differences: crt.guru is Commercial while s3viewer is Free, s3viewer is open-source. Use the table above to see where features, deployment and company size fit differ.

## Related comparisons

- [crt.guru vs Attack Surface Scan](https://cybersectools.com/compare/attack-surface-scan-vs-crtguru)
- [crt.guru vs ThreatDefence Integrated ASM](https://cybersectools.com/compare/crtguru-vs-threatdefence-integrated-asm)
- [crt.guru vs DarkInvader EASM Platform](https://cybersectools.com/compare/crtguru-vs-darkinvader-easm-platform)
- [s3viewer vs Attack Surface Scan](https://cybersectools.com/compare/attack-surface-scan-vs-s3viewer)
- [s3viewer vs ThreatDefence Integrated ASM](https://cybersectools.com/compare/s3viewer-vs-threatdefence-integrated-asm)
- [s3viewer vs DarkInvader EASM Platform](https://cybersectools.com/compare/darkinvader-easm-platform-vs-s3viewer)

## Alternatives to each

- [See all crt.guru alternatives](https://cybersectools.com/alternatives/crtguru)
- [See all s3viewer alternatives](https://cybersectools.com/alternatives/s3viewer)

---

Source: https://cybersectools.com/compare/crtguru-vs-s3viewer

For AI agents: each product above has its own Markdown page (add .md to its URL, for example https://cybersectools.com/tools/crtguru.md). Every CybersecTools shortlist is listed at https://cybersectools.com/shortlists.md.

More on crt.guru and s3viewer: funding, momentum, hiring and news, plus the full product and company record, are available through the Mandos MCP Server (paid plans), which connects to AI assistants: https://mandos.io/mcp?utm_source=cybersectools.com&utm_medium=compare-md