Grammarly is the best-known writing assistant, and since October 2025 it has been one product inside the Superhuman suite. Quill is the writing assistant built into WorkBOS. It underlines spelling, grammar, punctuation, wordiness and your company's own banned words as you type, and it lives where your business writing actually happens: CRM notes, message templates, sequences, proposals and Drive documents. No extension, no second subscription, and the underlines are computed entirely on your device. The one part that is not is whole-sentence correction, which sends each finished sentence to be checked; it is on unless the workspace or the person switches it off, and the underlines stay either way.
Grammarly is a superb general-purpose writing assistant with seventeen years of grammar tuning by its own count, a browser extension that follows you across the web, and, since March 2026, twenty-four non-English languages. If you need writing help in every app you use, keep it. Quill's bet is different: business writing happens inside your business tools, and the assistant there should know your house style, cost nothing extra, and be straight with you about what it sends. Two facts decide it for most teams. Grammarly is cloud-only, by its own documentation: its support pages say your computer must be connected to the internet for it to analyse your text. And on Grammarly Free, and on Pro bought self-serve from the website, the setting that lets Grammarly train its models on your text is ON unless you go and turn it off. Quill's underlines send nothing at all, on any plan, because the dictionary and the rules ship with the app and run in your browser, and we never train on your writing either way. We do the same thing Grammarly does in exactly one place and we say so: whole-sentence correction sends each finished sentence to the AI provider, it is on unless somebody switches it off, and both a workspace and an individual can switch it off without losing the underlines.
Swipe the table sideways to see the Grammarly column.
WorkBOS All-in-one + agents | Grammarly AI writing assistance | |
|---|---|---|
| Live spelling, grammar and punctuation underlines as you type | ||
| One-tap fixes, ignore, personal dictionary | ||
| Live checks run entirely on your device Grammarly is cloud software by its own documentation and cannot be used offline; Quill's spelling, grammar, punctuation and style underlines are computed in your browser and sent nowhere. Whole-sentence correction is the one part that cannot be: it sends the sentence, it is on unless somebody switches it off, and the workspace switch and the personal one are both on the Quill page | Partial | - |
| Your text is never used to train models Grammarly's training control is ON by default on Free and on self-serve Pro; it is off for Enterprise, Education and anything bought through their sales team | Partial | |
| Company style guide enforced in every suggestion Grammarly Pro includes one style guide and Enterprise unlimited; Quill applies yours in the AI pass and the live underlines both, on every plan that has Quill | Partial | |
| A banned word offers the word to use instead both put the substitute on the suggestion; Quill also underlines the term while you type in every WorkBOS text box, including Drive documents | ||
| A dictionary the whole workspace shares Grammarly has personal dictionaries and organisation-wide terms from Pro up; Quill shares the workspace dictionary from Pro up and, on top of it, learns two-word corrections the workspace keeps making | Partial | |
| Choose which kinds of suggestion you want Grammarly exposes 7 toggles in the app, an admin on-or-off per family, and free-text instructions in Go; Quill switches whole families on or off for the workspace or for one person, quiets a rule by itself after five ignores, and never lets anyone silence spelling and grammar | Partial | |
| Dismissed suggestions stay dismissed, and stay on your device the key carries a fragment of your own writing, so it is kept in your browser and never posted to a server | Partial | |
| Banned words underlined while typing | ||
| Wordiness, redundancy and clarity fixes with one tap | ||
| Sentence structure: agreement, verb form, comma splices, run-ons | ||
| Corrects a whole sentence, not only the words it recognises this is the half a rule engine cannot do. Ours is on unless the workspace or the person switches it off, and the sentence is sent to be checked; the underlines stay on the device either way. When only one word is wrong you get both: the word fix under the word and the whole corrected sentence beside it under "Or use the whole sentence". And the rewrite goes back through the grammar rules that found the mistake before you see it, so a correction that is still ungrammatical is refused rather than offered under a confident label | ||
| Inclusive-language suggestions | ||
| Document-level consistency: mixed British and American spelling, number style, serial commas Grammarly enforces the Oxford comma as a toggle; Quill also notices when a document is inconsistent with itself and offers the majority style | Partial | |
| AI rewrites, tone, summaries and drafting | ||
| Works inside collaborative documents without touching the file Quill paints its underlines outside the document, so co-authors never see them and nothing is saved into the file | Partial | |
| Lives inside your CRM, invoicing, HR, sequences and Drive Grammarly floats above other tools; Quill is native to the fields your business writes in | - | |
| Team analytics with kept-suggestion rate both report accepted suggestions; Quill breaks it down by rule and by outcome (accepted, ignored, added to dictionary) with no text stored, and the same numbers drive its adaptive quiet | ||
| Works in every app via a browser extension deliberate: Quill lives inside WorkBOS, and the WorkBOS MCP connector is how outside assistants reach your workspace | - | |
| Languages checked live Quill's live underlines are English only; Grammarly checks 24 non-English languages and 5 English dialects. Our AI pass drafts and translates in any language | Partial | |
| Plagiarism and AI-text detection needs a licensed corpus; planned as an integration, not improvised | - | |
| Depth of long-tail grammar catches Quill ships several hundred deterministic rules in twelve packs, across agreement, subject finding, noun number, verb form, tense, punctuation, confused words, pronoun case, possessives, sentence structure, wordiness and consistency, and the whole-sentence pass covers the rest. Measured: on a held-out set written by somebody who was not allowed to read the rules it catches 76%, on a second blind set it catches 58%, and on already-correct prose it paints 11.9 marks per 1,000 words. Grammarly has seventeen years of tuning here | Partial | |
| Snippets that expand from a typed shortcut type /thanks and press space; Quill snippets sit beside WorkBOS merge tokens, which fill on send surfaces like sequences and templates | ||
| Included in your business-software plan Grammarly is included in the Superhuman suite, which is a writing and communication suite; it is not part of the software that runs your CRM, invoicing, projects or HR | - | |
| Free training academy & certification no practitioner academy or certification; the partner directory is a reseller channel, and the company now trades as Superhuman | Partial | - |
Free forever for up to 5 seats (includes a metered taste of AI agents), Pro at $12/user/mo, Enterprise at $999/mo flat, and a White-label plan at $2,499/mo for unlimited resold sub-accounts. No card required to start.
Grammarly Free covers spelling, grammar and tone detection. Grammarly Pro is $12 per member per month billed annually, which is $144 up front, or $30 per member per month billed monthly; Enterprise is priced on request. Grammarly Pro replaced the old Grammarly Business plan and Premium accounts moved to Pro during 2025, though Premium is still sold in the app stores and Business is a live tier name inside the Superhuman suite, where Superhuman Pro at $12 per month billed annually includes full Grammarly. Quill is included with WorkBOS Pro and up at no extra per-seat charge. Pricing checked September 2026 against grammarly.com and superhuman.com; see those sites for the current figure.
If Grammarly is not the only tool you are weighing up, these cover the same ground against a different product.
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Comparison reflects each product’s primary positioning and publicly documented capabilities as of June 2026; capabilities and plans change. Grammarly is a trademark of its respective owner; this page is independent and implies no affiliation or endorsement.