Comparison
PromptShielder vs. Nightfall, Purview & DIY Regex: Honest Comparison
A candid feature-by-feature comparison including where each tool wins, where each loses, and where our own tool falls short.
PromptShielder Security Team· Applied cryptography & privacy engineering November 4, 2025 8 min read
| Capability | Nightfall | Purview | DIY Regex | PromptShielder |
|---|---|---|---|---|
| Deployment required | SaaS + agents | M365 tenant config | Self-built | None (browser) |
| Data leaves device | Yes (to Nightfall) | Yes (to Microsoft) | Depends | No — client-side only |
| Covers personal ChatGPT accounts | Partial | No | Only if you write it | Yes |
| Central audit trail | Yes | Yes | No | No (by design) |
| Detector quality | ML + rules | ML + rules | Regex-only | Rules + context heuristics |
| Cost floor | $$$ enterprise | Bundled with M365 | Engineering time | Free / low |
| Best fit | Mid-market+ w/ SecOps | M365-first orgs | Eng teams that maintain it | Individuals & small teams |
- DLP (Data Loss Prevention)
- A category of tools that inspects data leaving an organization and blocks or redacts sensitive content — typically deployed as a network proxy or endpoint agent.
- Client-side redaction
- Detection and substitution of sensitive strings before any network request leaves the browser. No server sees the pre-redacted text.
Nightfall
- Strengths: mature detectors, strong SaaS coverage, real MLPs for detection quality.
- Weaknesses: SaaS-first (data flows to Nightfall for scanning), needs procurement, priced for teams not individuals.
- Best for: mid-market and up with a security team that will run it.
Microsoft Purview
- Strengths: deep integration with Office, Edge, Teams and Copilot for M365; centrally administered; strong audit surface.
- Weaknesses: only fully useful inside the Microsoft stack; policy authoring has a learning curve; blind to Chrome + personal ChatGPT.
- Best for: M365 shops enrolling Copilot company-wide.
DIY regex
- Strengths: free, transparent, auditable.
- Weaknesses: brittle, high false-positive rate on names/orgs, requires ongoing maintenance.
- Best for: engineering teams that will actually maintain it.
PromptShielder
- Strengths: zero deployment, zero server, runs on the personal account and the unmanaged browser, covers 16 entity categories out of the box, custom terms for per-engagement literals.
- Weaknesses: no central enforcement, no audit trail across users, no policy-authoring surface for a security team.
- Best for: freelancers, consultants, small teams, and — as a compensating control — any company whose employees use LLMs on personal accounts.
The one control everyone should copy
Redact-before-send. Independent of vendor. Independent of tier. It is the one control that survives every architecture change the LLM ecosystem has thrown at us over the last two years.
Frequently asked
Do you plan a central admin console?+
It is on the roadmap for teams, deliberately opt-in — a lot of PromptShielder's value is that no telemetry leaves the device.
Can I combine PromptShielder with Purview?+
Yes. They operate at different layers.
Sources
Comparison