When you enter employee Social Security numbers, salaries, and hours into payroll software, you're handling some of the most sensitive data your business touches. A breach doesn't just mean a regulatory fine — it can expose your employees to identity theft and destroy trust you've spent years building. So the first question any small business owner should ask before adopting any payroll tool is: where does this data actually go?
Micro-Payroll is built on a local-first architecture. Every employee record, tax calculation, and pay stub you create is stored exclusively in your browser's built-in IndexedDB database — on your own device. Nothing is transmitted to a remote server, because there is no payroll data server. The app's servers only deliver the software itself; they never receive your employee records, SSNs, wage figures, or company EIN.
This guide explains exactly how that works, what it means for your data under US privacy law, what the real risks are (and how to manage them), and how Micro-Payroll compares to cloud-based alternatives on the privacy dimension.
What 'Local-First' Actually Means for Your Payroll Data
Cloud payroll software — Gusto, QuickBooks Payroll, ADP Run — encrypts data in transit and stores it on their servers. That's necessary for features like bank integrations and multi-device sync, but it also means your employees' SSNs and salary information lives on a third-party server that is, by definition, accessible to people outside your company.
Local-first is a different design philosophy. The Micro-Payroll app runs entirely inside your browser as a Progressive Web App. When you add an employee, that record is written to IndexedDB — the same storage mechanism your browser uses for offline email and bookmarked articles. The record never leaves your device unless you explicitly use the Backup feature to export a file, and even that export file stays on your local machine.
What the Micro-Payroll servers do handle: serving the JavaScript application code, authenticating your login session so your data syncs across browsers if you choose, and accepting payslip email requests. Employee names, SSNs, wage data, and tax calculations are never part of any server request.
You can verify this yourself. Open your browser's developer tools while using the app, switch to the Network tab, and run a payroll calculation. You'll see requests to fonts and static assets — but no POST request carrying your employee data.
How SSNs Are Protected: Encryption at Rest
Social Security numbers require a higher level of care than most other payroll data. Micro-Payroll encrypts each SSN individually using AES-256-GCM before it's written to IndexedDB. The encryption key is derived from your account credentials and stored separately from the encrypted value — so even if someone gains access to your device's browser storage, they cannot read SSNs without your login.
In practice, this works as follows. When you enter a new employee's SSN, the app encrypts it immediately in the browser before writing anything to storage. Only the last four digits are kept in plaintext, so the employee list can show '***-**-1234' without decrypting on every load. When you click the reveal button, the app decrypts that employee's SSN on demand and displays it temporarily. The full SSN is never stored in your browser's session memory any longer than necessary.
The ESD (Employment Security Department) CSV export — used for quarterly WA wage reporting to the EAMS portal — does include full SSNs, because the state requires them. That file is generated locally, downloaded directly to your device, and uploaded by you to the ESD portal. Micro-Payroll never has access to the generated file after you click Download.
What Are the Real Data Risks, and How Do You Manage Them?
Local-first doesn't mean risk-free. The risks are just different from cloud software, and they're largely within your control.
1. Device loss or browser reset — If you lose your device or clear browser data, your payroll records could be lost. The app's Backup & Restore feature (under Settings) exports a full encrypted backup file. Download a backup after every payroll run and store it somewhere safe — an external drive or encrypted cloud folder like a personal Keychain-synced iCloud Drive.
2. Shared or infected devices — IndexedDB data is scoped to the browser origin (micro-payroll.com), but another app running on the same device could read it if the device is compromised. Use payroll software only on a device you trust, and keep the OS and browser updated.
3. Phishing and account takeover — If someone logs into your Micro-Payroll account from another device, they can access any data you've synced. Use a strong, unique password and enable two-factor authentication on your email account — that's often the weakest link in any web app's security chain.
For most small businesses with one to ten employees, local-first payroll represents a significantly smaller attack surface than a cloud service, which adds a server, a database, a team of employees with access, and a set of API credentials to the threat model.
Privacy Laws and What They Mean for Your Payroll Tool
Under the California Consumer Privacy Act (CCPA) and similar state laws, businesses that collect and share personal information have disclosure and deletion obligations. When your payroll software stores employee data on its own servers, that software vendor becomes a service provider under CCPA — meaning they process personal data on your behalf and you need a data processing agreement with them.
With local-first payroll, there's no third-party service provider receiving employee personal data from the app. The data controller (you) and the data processor are the same person, which simplifies your CCPA and state data handling obligations considerably.
For employees, this means no payroll vendor data breach can expose their SSN or salary through Micro-Payroll. It doesn't eliminate all privacy risk — a breach of your device is still possible — but it removes the third-party server from the equation entirely.
Micro-Payroll is open source. The full application code is available on GitHub, which means any developer, security researcher, or auditor can verify these claims independently rather than relying on a vendor's word.
If keeping your employees' data off third-party servers matters to your business, try Micro-Payroll at micro-payroll.com. The calculator, payslip generator, and quarterly report tools are free, and your data stays in your browser.
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