The Only Sequence Diagram Tool That Never Uploads Your Diagrams
- Your diagram code is processed entirely in your browser, never uploaded to any server
- No account, no tracking, no analytics on your diagram content
- Safe for internal architecture, API secrets, and compliance-sensitive documentation
- Works offline after initial page load
Table of Contents
When you paste an internal architecture diagram into an online tool, think about what you are sharing. Service names, database schemas, authentication flows, internal API endpoints. For personal projects this does not matter. For enterprise software, it may violate compliance requirements. For security-sensitive systems, it is a genuine risk.
Our sequence diagram tool processes everything in your browser. Your diagram code never leaves your device. No server rendering, no cloud storage, no telemetry on the content you draw.
What Most Online Diagram Tools Actually Do
Popular online diagramming tools fall into three privacy categories:
Server-side rendering: You paste code in the browser. The browser sends it to their server. The server renders the diagram and returns an image. Your diagram code sits in their server logs, potentially their database. Examples: PlantUML Online (plantuml.com), sequencediagram.org.
Cloud storage: You create a diagram. The tool saves it to their cloud as part of your account. Diagrams are tied to your login, stored on their servers. Examples: Lucidchart, Canva, Figma (for diagram features).
Analytics and tracking: Even browser-based tools often send usage analytics. The diagram content itself may not be transmitted, but metadata about your usage (how often you create diagrams, what features you use, how long you spend) goes to analytics servers.
For most personal use cases, none of these matter. For internal enterprise documentation, legal contract workflows, healthcare system design, financial infrastructure diagrams, any of these can be a problem.
How This Tool Handles Privacy
Our sequence diagram tool is architected for zero data leakage:
- No account required. You cannot be identified if you never identified yourself.
- Client-side rendering. The Mermaid library runs in your browser. Your diagram code is processed by JavaScript on your device. Nothing is sent to any server for rendering.
- No diagram persistence. We do not store your diagrams. Close the tab, your work is gone (so save your Mermaid source if you want to keep it).
- No telemetry on content. Anonymous page-view analytics exist, but the content of what you type is never transmitted anywhere.
The simplest way to verify: open your browser's Developer Tools (F12), go to the Network tab, and use the tool. You will see the initial page load and the static asset downloads. You will not see any outgoing requests when you type diagram code or click Render. The rendering happens entirely in your browser's JavaScript engine.
This transparency matters. You do not have to trust our privacy policy. You can verify the behavior directly.
Sell Custom Apparel — We Handle Printing & Free ShippingWhen Privacy Matters for Sequence Diagrams
The following scenarios make browser-only processing necessary rather than just preferable:
Enterprise IT documentation. Sequence diagrams of internal services, authentication flows, and database interactions may be classified as sensitive architecture information. Company security policies often prohibit sharing these with external SaaS tools.
Regulated industries. Healthcare (HIPAA), financial services (SOC 2), government contractors (FedRAMP), and defense industry workflows often have explicit controls on third-party data processing. A tool that never transmits your content avoids these compliance concerns entirely.
Security research and penetration testing. Documenting attack chains, exploit sequences, or vulnerability disclosure processes requires absolute confidentiality until disclosure. Uploading these to a third-party server is unacceptable.
Mergers and acquisitions work. System diagrams for due diligence, integration planning, or post-acquisition architecture reviews are commercially sensitive. Even anonymized versions can reveal strategy.
Startups in stealth mode. Pre-launch product architecture, investor pitches with system diagrams, or competitive intelligence documents should not be on third-party servers that might be subpoenaed, hacked, or acquired by a competitor.
Can You Use This Tool Offline?
After the initial page load, the tool can run without an active internet connection. The Mermaid library, CSS, and JavaScript are cached by your browser. Opening the tool, typing a diagram, and exporting all work without network access.
Limitations of offline use:
- First load requires internet (to download the page and library)
- Browser cache may expire; if the cache is cleared, the next use requires internet
- If the browser tab is closed, reopening may try to fetch updates (most browsers use cached versions if offline)
For guaranteed offline use, the Mermaid CLI (mmdc) runs locally on your machine without any web component. Install once, use offline forever. But for the vast majority of users who have internet access, the browser tool is simpler and provides the same privacy guarantees.
If your organization air-gaps certain machines (no internet access at all), a locally-hosted Mermaid instance is the only way to get sequence diagrams on those machines. Ask your IT team; many large organizations have internal Mermaid mirrors for exactly this use case.
Privacy Comparison With Other Tools
| Tool | Content Uploaded? | Account Required? | Stores Diagrams? |
|---|---|---|---|
| This Tool | No | No | No |
| PlantUML Online | Yes (for rendering) | No | No |
| Mermaid Live Editor | No (client-side) | No | Via URL sharing |
| Lucidchart | Yes | Yes | Yes |
| Draw.io Web | No (local storage option) | No | Optional cloud |
| Figma/FigJam | Yes | Yes | Yes |
| Sequencediagram.org | Yes (for rendering) | No | No |
Mermaid Live Editor is also client-side, but its URL-sharing feature encodes your diagram in the URL, which means if you share a link, the recipient can see your full diagram. Our tool has no URL-based persistence, so there is no shareable-link side channel.
For maximum paranoia: open our tool, disconnect from the internet, use the tool offline for your diagram, export the SVG, and only reconnect after you have closed the tab. The tool works, and during your session there is literally no outgoing traffic.
Your Diagram Code Stays Yours
No account, no upload, no tracking. Draw internal architecture with zero data leakage.
Open Free Sequence Diagram MakerFrequently Asked Questions
Does this sequence diagram tool upload my diagrams to your servers?
No. Your diagram code is processed entirely in your browser using JavaScript. The Mermaid rendering library runs client-side. We do not transmit, store, or log the content of your diagrams. You can verify this in your browser Developer Tools Network tab.
Is it safe to create internal architecture diagrams with an online tool?
Only if the tool processes content client-side. Server-side rendering tools (like PlantUML Online) send your code to their servers. Our tool runs everything in your browser. Your internal architecture details never leave your device. This makes it suitable for enterprise, healthcare, financial, and compliance-sensitive documentation.
Can I use this tool for HIPAA or SOC 2 compliant workflows?
For the tool itself: yes, because no data leaves your browser. For your overall compliance posture, consult your compliance team about any web-based tool. Since no content is transmitted to us, the tool does not introduce third-party data processing into your workflow.
Does this tool work offline?
After the initial page load, yes. Your browser caches the tool assets. You can work on diagrams without internet access. For guaranteed offline use on air-gapped machines, a local Mermaid CLI installation is the most reliable option.
