Skip to main content

On-Premises Grammar Checkers and Language Model Assistants

Language Model Assistants

Language model assistants (or writing assistants), including grammar checkers such as Microsoft Editor and Grammarly, can help individuals and business teams:

  1. Keep messages error-free and professional.
  2. Save time, especially if they have to compose personalized replies.

For business teams, such systems also have the ability to:

  1. Ensure consistent messaging across a team.
  2. Provide managers with analytics so that they can give feedback to their team members.

Software as a Service (SaaS)

Today, most software services, including services such as Microsoft Editor and Grammarly, are cloud-based Software as a Service (SaaS). This has many benefits, including:

  1. Little upfront commitment is required. The client does not need to purchase extra servers to roll out the service, and costs are month-to-month or year-to-year.
  2. The service continuously improves. As upgrades and new features are added, they automatically become available to users.
  3. As SaaS providers handle deployment and integration, usually very little developer time is required from the client and it's assumed that the SaaS provider will handle scaling.

As vendors may handle sensitive customer data, SaaS services should also be checked for security standards and compliance. This includes commonly agreed upon standards such as American Institute of CPAs (AICPA) SOC 2 certification (which includes two types, Type I and Type II) as well as the ISO 27001 certification.


Requirements go beyond such external audits, however. You've likely already encountered regulations such as:

  • European General Data Protection Regulation (GDPR)
  • California Consumer Privacy Act (CCPA), or
  • Philippines Data Privacy Act of 2012.

Common compliance standards (SOC 2, HIPAA, PCI DSS)

A few of the common compliance standards.

Such regulations impose requirements on businesses that process sensitive customer information, including requirements on data transfer, storage, documentation, and user consent. More regulations are looming.

Further, some industries are unable to share data without meeting compliance standards. For example:

  • Healthcare: HIPAA (Health Insurance Portability and Accountability Act) compliance is required for businesses for the secure processing of PHI (protected health information) / ePHI (electronic protected health information). Sapling offers HIPAA-compliant spelling and grammar checkers in the cloud or self-hosted.
  • Finance: PCI DSS (Payment Card Industry Data Security Standard) is a strict security standard for organizations that handle credit card information.

Despite the convenience of SaaS, self-hosted/on-premises deployments may make sense for your business depending on regulations and business requirements in order to keep data security and privacy in-house.

Assuming you're looking for one, which vendor should you go with? This article covers some of the different vendors, benefits and drawbacks of each, and the factors that should go into your decision.


Spoiler: If you're looking for a vendor that will meet your requirements, you can check out Sapling's integrations or contact us.


Some of the aforementioned cloud-based grammar checkers like Microsoft Editor and Grammarly do not have self-hosted or on-premises offerings. As of January 2022, here are some common grammar checkers/writing assistant tools that offer self-hosted deployments:

  • Grammark
  • LanguageTool
  • Sapling
  • WebSpellChecker

Let's go through the offerings one at a time.


Grammark is a grammar checker tool created by Mark Fullmer. It currently includes over 7000 grammar rules in its database. The source code is available on GitHub, making it an open source option.

Grammark is primarily implemented in JavaScript, meaning that it should be easy to get running in the browser. However, given it uses a database of rules, it is likely restricted to certain types of errors, but not others. For example, on the Grammark webpage it states that subject-verb agreement errors are not handled. In the "Resources" section of the Grammark website, a list of error mappings is provided.


LanguageTool is proofreading software originally developed by Daniel Naber and released in 2005 as part of his 2003 thesis.

LanguageTool's core system is free and open-source. Unlike systems such as Grammarly, languages supported include English, German, Spanish, French, and Portuguese. For teams with 250 or more uses, LanguageTool provides an on-prem option.

With its ability to support multiple languages, however, comes some limitations in the types of suggestions that LanguageTool offers. On benchmarks, we have found that its database of rules does not provide as good coverage as systems such as Sapling.


Sapling is the language model copilot for businesses. Its technology is based on research published in the Stanford AI lab.

The most recently developed of the solutions described here, Sapling is especially geared towards business teams such as customer support teams or inside sales teams. It includes not only grammar checking and other writing assistance software for agents, but also a dashboard with actionable insights for managers.

In addition to its focus on customer-facing teams, Sapling provides rich writing suggestions through its use of machine learning models trained on millions of sentences. Sapling also offers an on-prem option for businesses. As of this writing, it is not open source.


WebSpellChecker has been available as since at least 2000, but was refounded as WebSpellChecker in 2016. WebSpellChecker is an add-on for rich text editors that provides spelling and grammar check functionality.

WebSpellChecker works with common editors such as CKEditor, TinyMCE, and Quill. It has dictionaries for over 100 languages, and supports self-hosted deployments.

As of this writing, additional suggestions beyond spell checking and browser integrations do not appear to be publicly available.

Which solution is best?

WebSpellCheckerMultiple languages, integration with rich text editorsNon-spelling suggestions limited, browser integrations not found
SaplingPowerful AI models, designed for business teams, many integrationsNot open source
LanguageToolMultiple languages, open source option, many integrationsBased on database of rules
GrammarkOpen source, JS libraryBased on database of rules, not many integrations

Comparison of self-hosted providers.

For those looking for an self-hosted/on-premise grammar checker similar to Grammarly or Microsoft Editor, the best solution depends on your use case:

  • For those who need support for multilingual support, we recommend LanguageTool or Sapling.
  • For those looking to integrate with specific editors and mainly want spell check, we suggest trying WebSpellChecker.
  • For those keen on open source and are looking for a system that is implemented in JavaScript, we recommend Grammark.
  • For businesses with customer-facing teams, we recommend Sapling (us).


We recommend you reach out to the different vendors and make your own comparison.

Obviously, we're biased. You can reach out to us for a trial here:

Or give Sapling a try with one of our integrations.

Other tools? Let us know: