Grammarly

AI writing assistant for grammar, style, clarity, and generative content creation

Lumo (Proton)

Privacy-first AI assistant from the makers of ProtonMail, with Swiss jurisdiction and zero-access encryption

Grammarly

Strong

17/25

Lumo (Proton)

Excellent

23/25

Score Breakdown

DimensionGrammarlyLumo (Proton)

Data Residency

Where is your data stored and processed?

Grammarly: Data hosted exclusively in US AWS East; no EU or regional residency option

Lumo (Proton): Data hosted in Proton's own data centres in Germany and Norway. Zero-access encryption means even Proton cannot read conversation content. No US infrastructure dependency.

2/5

Data hosted exclusively in US AWS East; no EU or regional residency option

5/5

Data hosted in Proton's own data centres in Germany and Norway. Zero-access encryption means even Proton cannot read conversation content. No US infrastructure dependency.

Legal Jurisdiction

Which laws govern the company and your data?

Grammarly: US Delaware corporation subject to CLOUD Act; GDPR compliance via SCCs and DPA

Lumo (Proton): Swiss incorporation provides one of the strongest privacy jurisdictions globally. Outside US CLOUD Act reach. Swiss FADP and GDPR adequacy. Proton has a decade-long track record of defending user privacy.

2/5

US Delaware corporation subject to CLOUD Act; GDPR compliance via SCCs and DPA

5/5

Swiss incorporation provides one of the strongest privacy jurisdictions globally. Outside US CLOUD Act reach. Swiss FADP and GDPR adequacy. Proton has a decade-long track record of defending user privacy.

Data Retention & Training

Is your data used for model training?

Grammarly: User data not sold; limited processing for product improvement with user controls

Lumo (Proton): Zero-access encryption on conversations. User data explicitly never used for model training. Open-source code enables independent verification of privacy claims.

4/5

User data not sold; limited processing for product improvement with user controls

5/5

Zero-access encryption on conversations. User data explicitly never used for model training. Open-source code enables independent verification of privacy claims.

Certifications

ISO 27001, SOC 2, Cyber Essentials, etc.

Grammarly: Extensive certification: SOC 2 Type II, ISO 27001/18/701, ISO 42001

Lumo (Proton): ISO 27001 and SOC 2 at Proton AG organisational level. Strong for a consumer-facing privacy product. ISO 27701 would further strengthen the posture.

5/5

Extensive certification: SOC 2 Type II, ISO 27001/18/701, ISO 42001

4/5

ISO 27001 and SOC 2 at Proton AG organisational level. Strong for a consumer-facing privacy product. ISO 27701 would further strengthen the posture.

Regulatory Fit

Suitability for regulated industries and professional services

Grammarly: Strong enterprise compliance posture; US-only hosting limits suitability for EU data residency mandates

Lumo (Proton): Excellent fit for privacy-sensitive professionals in legal and financial services. Swiss jurisdiction, zero-access encryption, and no training on user data address key regulatory concerns. Not EU-incorporated but GDPR adequate.

4/5

Strong enterprise compliance posture; US-only hosting limits suitability for EU data residency mandates

4/5

Excellent fit for privacy-sensitive professionals in legal and financial services. Swiss jurisdiction, zero-access encryption, and no training on user data address key regulatory concerns. Not EU-incorporated but GDPR adequate.

Total Score

17/25

23/25

Best For

Grammarly

Best for organisations requiring broad certification coverage (SOC 2 Type II, ISO 27001, ISO 27018); privacy-conscious teams who need strong data retention controls; teams on a tight budget.

Lumo (Proton)

Best for EU-headquartered organisations needing maximum data sovereignty; regulated industries (legal, financial-services); privacy-conscious teams who need strong data retention controls; organisations that need self-hosted or on-premise deployment; teams on a tight budget.

Detailed Comparison

Grammarly vs Lumo (Proton): Trust & Compliance Comparison

Grammarly (Grammarly, Inc., US) scores 17/25 overall with a Silver (Strong) trust badge. AI writing assistant for grammar, style, clarity, and generative content creation. Lumo (Proton) (Proton, CH) scores 23/25 with a Gold (Excellent) trust badge. Privacy-first AI assistant from the makers of ProtonMail, with Swiss jurisdiction and zero-access encryption.

Dimension-by-Dimension Breakdown

#### Data Residency

Lumo (Proton) leads with 5/5 vs 2/5.

●Grammarly (2/5): Data hosted exclusively in US AWS East; no EU or regional residency option

●Lumo (Proton) (5/5): Data hosted in Proton's own data centres in Germany and Norway. Zero-access encryption means even Proton cannot read conversation content. No US infrastructure dependency.

#### Legal Jurisdiction

Lumo (Proton) leads with 5/5 vs 2/5.

●Grammarly (2/5): US Delaware corporation subject to CLOUD Act; GDPR compliance via SCCs and DPA

●Lumo (Proton) (5/5): Swiss incorporation provides one of the strongest privacy jurisdictions globally. Outside US CLOUD Act reach. Swiss FADP and GDPR adequacy. Proton has a decade-long track record of defending user privacy.

#### Data Retention & Training

Lumo (Proton) leads with 5/5 vs 4/5.

●Grammarly (4/5): User data not sold; limited processing for product improvement with user controls

●Lumo (Proton) (5/5): Zero-access encryption on conversations. User data explicitly never used for model training. Open-source code enables independent verification of privacy claims.

#### Certifications

Grammarly leads with 5/5 vs 4/5.

●Grammarly (5/5): Extensive certification: SOC 2 Type II, ISO 27001/18/701, ISO 42001

●Lumo (Proton) (4/5): ISO 27001 and SOC 2 at Proton AG organisational level. Strong for a consumer-facing privacy product. ISO 27701 would further strengthen the posture.

#### Regulatory Fit

Both score equally at 4/5.

●Grammarly (4/5): Strong enterprise compliance posture; US-only hosting limits suitability for EU data residency mandates

●Lumo (Proton) (4/5): Excellent fit for privacy-sensitive professionals in legal and financial services. Swiss jurisdiction, zero-access encryption, and no training on user data address key regulatory concerns. Not EU-incorporated but GDPR adequate.

Certifications at a Glance

Certification	Grammarly	Lumo (Proton)
ISO 27001	Yes	Yes
ISO 27018	Yes	No
ISO 27701	Yes	No
ISO 42001	Yes	No
SOC 2	No	Yes
SOC 2 Type II	Yes	No

Overall Verdict

Lumo (Proton) has a clear trust advantage, scoring 23/25 compared to Grammarly's 17/25. Lumo (Proton) particularly excels in data residency, legal jurisdiction, data retention & training.

Frequently Asked Questions

Which is better for EU compliance, Grammarly or Lumo (Proton)?

Grammarly has a TrustKit score of 17/25 while Lumo (Proton) scores 23/25. Lumo (Proton) currently rates higher across data residency, legal jurisdiction, data retention, certifications, and regulatory fit.

How do Grammarly and Lumo (Proton) compare on data residency?

Grammarly scores 2/5 for data residency (Data hosted exclusively in US AWS East; no EU or regional residency option), while Lumo (Proton) scores 5/5 (Data hosted in Proton's own data centres in Germany and Norway. Zero-access encryption means even Proton cannot read conversation content. No US infrastructure dependency.).

Are Grammarly and Lumo (Proton) GDPR compliant?

Both tools are assessed across five compliance dimensions. Grammarly has a regulatory fit score of 4/5 and Lumo (Proton) scores 4/5. Check the full comparison above for a detailed breakdown.

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