Networking
Free Subnet Calculator: IPv4 CIDR, Netmask & Host Range
Subnetting is the foundation of modern TCP/IP networking, cloud VPC routing, and network segmentation. Calculating IP masks, CIDR…
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Developer
Base64 Encode & Decode: Instant Online String Converter
Base64 encoding is widely used across API authentications, JWT payloads, email MIME attachments, and inline image data URIs.…
Network
Bandwidth & Download Time Calculator: Mbps to MB/s Converter
Understanding the difference between megabits per second (Mbps, advertised by internet service providers) and megabytes per second (MB/s,…
Developer
User Agent Checker: Browser Signature & Device Inspector
Every HTTP request sends a User-Agent header specifying the client browser version, rendering engine, and operating system architecture.…
Network
DNS Lookup & Propagation Checker: A, MX, TXT & NS Records
Diagnose domain name resolution, verify Google Workspace or Microsoft 365 mail exchange (MX) records, and audit SPF/DKIM TXT…
Developer
HTTP Header Checker: Audit Response Headers & Security Status
Inspect server response codes (200, 301, 302, 404, 500), evaluate HTTP Strict Transport Security (HSTS), Content-Security-Policy (CSP), and…
Security
SSL Certificate Checker: Verify Expiration Date & TLS Chain
An expired SSL/TLS certificate triggers severe browser security warnings, destroying organic visitor trust. 99tools SSL Certificate Checker tests…
Security
Network Port Scanner: Audit Common Ports & Socket Services
Auditing open TCP socket ports helps network administrators identify exposed services, misconfigured firewalls, and server security vulnerabilities. 99tools…
Featured
Flagship
Free Online Diagram Maker & Flowchart Studio
Creating software architecture diagrams, system schematics, flowcharts, and technical wireframes online has long been complicated by commercial subscriptions,…
Featured
Popular
Color Palette Studio — Free Spacebar Generator, UI Visualizer & Contrast Matrix
Creating cohesive, accessible color palettes has long been hampered by intrusive paywalls and limitations. Many online palette tools…