Terms of Service
1. Agreement to these terms
These Terms of Service ("Terms") are an agreement between you and Quodsi LLC ("Quodsi," "we" or "us"), 330 E Liberty, Ann Arbor, MI 48104. They apply to your use of Quodsi software, including Quodsi for Lucidchart and Quodsi for Draw.io, and to the Quodsi website at quodsi.com (together, the "Services").
By creating an account, installing or opening Quodsi, or otherwise using the Services, you agree to these Terms and to our Privacy Policy. If you use the Services for an organization, you confirm that you have authority to bind it, and "you" includes that organization. If you do not agree, do not use the Services.
2. The Services and Lucidchart
Quodsi adds discrete-event simulation to process diagrams. You convert a diagram into a simulation model, enter inputs such as arrival rates, processing times and resource capacity, and run scenarios to see estimated performance.
Quodsi for Lucidchart runs inside Lucidchart and requires a Lucidchart account. Your use of Lucidchart is governed by Lucid's own terms, not these Terms. Quodsi for Draw.io runs in your web browser at drawio.quodsi.com and requires no installation.
Quodsi is an independent product. It is not made, sponsored or endorsed by Lucid Software or by the makers of draw.io (diagrams.net). Lucidchart and draw.io are trademarks of their respective owners and are used only to describe compatibility.
3. Accounts
Some features, including the guided tour and running simulations, require a free account. You must give accurate information and keep it current. You must be at least 18, or the age of majority where you live, to create an account.
Sign-in uses one-time codes sent to your email address, so you are responsible for keeping that email account secure and for activity under your account. Tell us promptly at support@quodsi.com if you believe someone has accessed your account without permission.
4. Plans, billing and cancellation
Quodsi offers a Free plan and a paid Professional plan. Features and limits for each plan are described on quodsi.com. We may change Free plan features or limits, and we will tell you if we make a significant reduction.
- Professional plan: Quodsi Professional costs $99 per month. It is available only by contacting us at support@quodsi.com. There is no self-serve upgrade in the product.
- Billing: Professional is billed monthly in advance and renews automatically each month until you cancel. Prices do not include taxes.
- Cancellation: You can cancel at any time by emailing support@quodsi.com. Cancellation takes effect at the end of the current monthly billing period, and you keep access until then.
- Refunds: Fees are non-refundable, and we do not give partial refunds for unused time, except where the law requires or where we charged you in error. If you think you were charged in error, email support@quodsi.com within 30 days.
- Price changes: We will give at least 30 days' notice before changing the price of Professional for an existing customer. The change applies from your next renewal, and you can cancel before it takes effect.
5. License and restrictions
Subject to these Terms, we grant you a limited, non-exclusive, non-transferable, revocable license to use the Services for your internal business or personal purposes. You may use the diagrams, models and results you create for your own work and share them with others.
You may not:
- copy, modify or create derivative works of the Services, except as the law allows
- reverse engineer, decompile or try to extract source code or underlying models, except as the law allows
- resell, sublicense or offer the Services to others as a competing service
- remove proprietary notices
- get around plan limits, access controls or security measures
6. Your content and data
"Your content" means the diagrams, simulation models, inputs, results and messages you submit to or create with the Services. You own your content.
You give us permission to host, process and display your content only as needed to run, secure, support and improve the Services and to provide the features you use, including the AI helper described below. As our Privacy Policy explains, diagrams and models are stored on Quodsi servers hosted on Microsoft Azure, and we keep them until you ask us to remove them. To request removal, email support@quodsi.com.
You are responsible for your content and for having the right to use it. Quodsi does not need personal data to run a simulation, so please do not include any in your diagrams or models.
We may use usage data that does not include the contents of your diagrams or models, such as sign-ins and simulation runs, to operate and improve the Services.
7. AI features
The AI helper guides you as you add data to the shapes in your diagram. Using it is optional, and you can skip it and enter data yourself.
When you use the helper, you choose the AI model. Your current diagram and the messages you send are shared with the provider of that model so it can respond. Our Privacy Policy states that diagram content sent to the helper is not used to train those providers' models.
AI output can be incomplete or wrong. Review every suggestion before you accept it. You stay in control of the numbers and are responsible for the inputs in your model. Do not put confidential or personal information in helper messages unless you are comfortable sending it to the provider you selected.
8. Simulation results are estimates
Quodsi produces estimates, not predictions or guarantees. Results depend on the inputs, assumptions and structure of the model you build, and on random variation within the simulation. Real processes may behave differently.
You are responsible for checking that your model reflects your process and for the decisions you make from the results, including recommendations you give to others. Quodsi does not provide professional engineering, financial, legal or operational advice. Do not rely on results alone where an error could cause injury or serious loss.
9. Acceptable use
You agree not to:
- break the law or infringe anyone's rights while using the Services
- upload malware, or probe, disrupt or overload the Services
- access another person's account, data or content without permission
- scrape or automate the Services beyond normal use
- create or share unlawful, harmful or deceptive content
- suggest that Quodsi is affiliated with, or endorsed by, Lucid Software or any other third party
10. Our intellectual property and your feedback
Quodsi and its software, design, text, logos and documentation are owned by us or our licensors and protected by law. These Terms give you no ownership of them, and no right to use our name or logo except to refer to the Services accurately.
If you send us feedback or suggestions, we may use them without obligation to you.
11. Suspension and termination
You may stop using the Services at any time and may close your account by emailing support@quodsi.com.
We may suspend or end your access if you breach these Terms, if your use creates risk or legal exposure for us or others, or if we discontinue the Services. Where practical, we will give notice first. If we discontinue a paid plan, we will refund any prepaid fees for the unused period.
When your access ends, your right to use the Services ends. We handle your diagrams and models as described in the Privacy Policy, and you can ask us to remove them. Sections that by their nature should continue, such as ownership, disclaimers, limits on liability and governing law, continue after termination.
12. Disclaimers, limits on liability and indemnification
Disclaimer. The Services are provided "as is" and "as available." To the extent the law allows, we disclaim all warranties, express or implied, including merchantability, fitness for a particular purpose, accuracy of results and non-infringement. We do not promise that the Services will be uninterrupted or error-free.
Limit on liability. To the extent the law allows, Quodsi will not be liable for indirect, incidental, special, consequential or punitive damages, or for lost profits, revenue, data or goodwill, arising out of or related to the Services. Our total liability for any claim is limited to the greater of the amount you paid us for the Services in the 12 months before the claim or US$100. Some places do not allow certain limits, so some of these may not apply to you.
Indemnification. You will defend and indemnify Quodsi against third-party claims arising from your content or your breach of these Terms.
13. Changes, governing law and contact
Changes. We may update these Terms. We will post the new version on this page with a new effective date and, for material changes, tell you by email or in the product. If you keep using the Services after the effective date, you accept the changes.
Governing law. These Terms are governed by the laws of the State of Michigan, without regard to its conflict-of-law rules. You and we agree that disputes will be brought in the state or federal courts located in Washtenaw County, Michigan.
General. These Terms and the Privacy Policy are the entire agreement between you and us about the Services. If a provision is unenforceable, the rest stays in effect. You may not assign these Terms without our consent. We may assign them in a merger or sale. Not enforcing a provision is not a waiver of it.
Contact. Questions about these Terms: support@quodsi.com or quodsi.com/support. Quodsi, 330 E Liberty, Ann Arbor, MI 48104.
Effective date: November 12, 2026