EU Sovereignty Score
Self-hosted / open sourceWriting Assistance & GrammarHeadquarters: US

Harper: sovereignty score and 8 European alternatives

Harper is an open-source grammar checker that runs entirely on your own device. It checks spelling, capitalisation, awkward phrasing and grammar, without an LLM and without a cloud connection. According to the site there is no telemetry and writing is never used to train models. It is available as a language server, JavaScript library, Rust crate, browser extension and via integrations with VS Code, Obsidian, Neovim and WordPress. It is an alternative to cloud services such as Grammarly.

Harper is published under the Apache-2.0 licence and developed on GitHub under the Automattic organisation; the site shows "© Automattic Inc.", a company with a mailing address in San Francisco. Because checking runs locally, your text does not leave the device and there is no vendor cloud where data is stored. The company is nonetheless subject to US jurisdiction. For European organisations the combination of open source and local processing is relevant, because the code can be inspected and deployed independently.

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Sovereignty score
69 / 1000 = high exposure
100 = sovereign
  • Jurisdiction SOV-210
    Headquartered in the US: CLOUD Act and FISA 702
  • Data residency SOV-3100
    No hosting in Europe (US)
  • Cryptographic key sovereignty SOV-390
    Self-hostable: encryption keys under your own control
  • Freedom from lock-in SOV-680
    Open source: low switching costs
  • Source & runtime sovereignty SOV-4 · SOV-665
    Source code auditable, forkable and self-hostable

SOV codes: the matching objective in the European Commission's Cloud Sovereignty Framework. Official source

How the score is calculated

Facts and evidence

Last checked October 12, 2026
Headquarters
US (US)Verified by hand
EU adequacy decision
Only for companies individually certified under the EU-US Data Privacy FrameworkVerified by hand
Sovereignty model
Open-source, distributedVerified by hand
Data hosting
USVerified by hand
Open-source
YesVerified by hand
GDPR-compliant
NoVendor-stated
Category
Writing Assistance & Grammar
Type
Product
Website
writewithharper.com ↗

How we verify · Something wrong? Suggest a correction

Top EU-based & GDPR-compliant alternatives to Harper

The European alternatives to Harper come from our knowledge base of over 8,000 vendors. We only list vendors headquartered in the EU or the EEA; fully European-owned vendors rank before vendors with a foreign owner. For each alternative you see the country, the open-source status and a short description.

Score per alternative: 0 = high exposure, 100 = sovereign

24 European Writing Assistance & Grammar vendors are in the catalogue. View the whole category · Submit an alternative · View category on the map

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Why digital sovereignty matters with Harper

Harper is headquartered in the United States. US vendors fall under the CLOUD Act and FISA 702: US authorities can compel access to data, even when that data sits in a European data centre. That is the core of the jurisdictional exposure in our model.

Harper hosts data outside the EU (US). Personal data therefore leaves the EU, which requires a transfer mechanism under the GDPR and pulls the data residency score down.

Harper is open source. You can audit the source code, self-host the software and keep the encryption keys under your own control. Switching is easier because data and software are not tied to a single party.

What this means for your organisation depends on your whole stack and context. The free assessment weighs Harper together with your other vendors and gives a total score, a heatmap and the main risk drivers.

Frequently asked questions

What is the best European alternative to Harper?

It depends on your use case. Strong EU alternatives to Harper include CKEditor, Congree and contentbird. On this page you can compare 8 EU alternatives by jurisdiction, data residency and open-source status.

Are there open-source alternatives to Harper?

Yes. Open-source EU alternatives to Harper include CKEditor, ghostwriter, Grammalecte and Kate. These keep your data fully under your own control and let you self-host if you want to.

Is Harper GDPR-compliant and where is the data hosted?

Harper is headquartered in US and hosts data in US. Its GDPR compliance is limited or unclear. For full EU data residency the EU alternatives on this page usually offer more certainty.

Details and sources

Verified by handHeadquarters, owner, hosting locations and licence have been checked by us against public sources. Free of charge and for every vendor, not a paid label. Nothing in this knowledge base is taken over automatically. Last checked on October 12, 2026.

Sources

Public sources used in the latest check of this record.

Compliance evidence

The links below point to the vendor's own public documents. We only record what we found: a missing link means "not found publicly", not "not compliant".

No public compliance evidence has been recorded for this vendor yet. Do you know its DPA or subprocessor list? Something wrong? Suggest a correction

Digital sovereignty in Writing Assistance & Grammar

Writing Assistance & Grammar: Grammar checking, spell checking, style advice and AI writing assistants. In this category the choice of vendor determines who has legal access to your data, where that data lives and how easily you can switch later.

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8 European alternatives to Harper — GDPR-compliant & EU-hosted · EU Sovereignty Score