Subtext vs Grammarly for personal messages and tone checking

Grammarly and Subtext overlap on one job and are built around two different ones. Grammarly, made by the company now called Superhuman, is an always-on writing assistant that sits where you already type, positioned for email, documents and work. Subtext is an app you bring one message to, built around reading a whole personal conversation and drafting the reply.

I co-founded Subtext, so weigh every product claim here accordingly. Every Grammarly fact below comes from Grammarly’s own documentation and every Subtext fact from our site, our store listing and the app itself, all checked 23 September 2026. No independent test compares the two, and none evaluates Subtext at all.

This is the head-to-head only. Who should leave Grammarly, and for what and what Apple, Google, Samsung and the chatbots do to your messages cover the wider field. This page prints no prices, because the sources I checked disagree on Grammarly’s monthly price.

The comparison by job, with no winner

I compare Grammarly and Subtext by job. For spelling and grammar corrected as you type, across a browser, Word, Outlook, Slack and a phone keyboard, Grammarly is designed for it (Grammarly’s product offerings)¹, and Subtext does not sit where you type. For long documents and workplace writing with style guides and admin controls, Grammarly again (Superhuman Suite pricing and plans)². For a personal conversation you can screenshot or paste, or a voice note that has to become a written reply, we designed Subtext for that job, and we found no Grammarly documentation of that workflow.

The overlap is tone. Grammarly detects the tone of your own text on every plan and suggests changes, with a limited number on the free plan². Subtext marks the words in your draft that could read wrong, names the feeling underneath, and offers three versions, each showing how much of your wording it changed (Subtext: the AI tone checker for personal messages)³.

The table below puts Grammarly and Subtext side by side, using each maker’s own sources.

Subtext’s co-founder wrote this table and checked its facts on 23 September 2026. It is a description, not a ranking. No independent test compares Grammarly and Subtext or evaluates Subtext at all, and neither tool can predict how a specific person will react. Neither language count says anything about quality.

Grammarly as its documentation describes it

Grammarly is a general writing assistant. On 29 October 2025 the company behind it renamed itself Superhuman; the writing product kept its name (Grammarly Rebrands Company as Superhuman, Introduces Superhuman Suite and Superhuman Go)⁴. It runs as Windows and Mac apps, as browser extensions, and as iPhone, iPad and Android apps with a keyboard, inside Word, Outlook, Slack and Gmail¹.

Its documented features, checked 23 September 2026: spelling and grammar correction on every tier, including Free; tone detection on every tier, with tone suggestions limited on Free; sentence rewrites; on-demand AI composition; paragraph rewrites and translation in a couple of dozen languages; and team controls such as style guides, single sign-on and audit logs². Paid plans add a voice profile learned from your writing (Introducing voice features)⁵. Reader Reactions, a document-level agent with a limited daily allowance on Free, simulates how a chosen kind of reader might take a piece of writing (Reader Reactions user guide)⁶. Read together, that is a tool built mainly for work; nothing we found in its documentation is written around a text to your sister.

Subtext and what we built it for

Subtext is an app you bring one message to. You type a draft, paste text or a screenshot of the conversation, or record a voice note, and it reads the whole exchange, not only your line³. For a draft you wrote, it marks the exact words that could land as harsh, cold, passive-aggressive, vague or over-apologetic and names the feeling underneath, watching for 48 kinds of trigger and reading from a vocabulary of 51 emotions; every flag is a “could read as”, never a verdict. Then it offers three versions: one close to what you wrote, one warmer, one shorter and clearer. Each carries a safe-to-send badge or a check-before-sending note. It never sends anything. You copy the version you choose.

Subtext has two limits I should state plainly. Its 48 triggers and 51 emotions are our own vocabulary, untested by anyone outside the company, as are the score and the rewrites. And the one outcome figure I can offer is an anecdote. In our own use, Subtext cuts the time a hard message takes by about 90 percent. The longer version is what the Subtext app is, who it is for and when to use it.

The case for a tone checker is the hard message

The research on misread personal texts is narrower than tone-tool marketing, Subtext’s included, tends to imply. Pollmann and Roos had people rate the tone of real text messages from a friend and real work or study emails, then asked the actual senders what they had intended. The two sides’ ratings of how positive or negative a message was, in the authors’ words, “align very well”, with “no indication for misunderstanding” (“I get u”. People correctly interpret the tone of text messages and emails)⁷. It is a single paper of two studies, it measured only valence, and its messages were mostly replies and feedback rather than emotional ones. But in that paper, routine texts between people who knew each other were mostly read as meant.

The claim that holds up for Grammarly or Subtext is help where the message is hard or the context is thin. We found nothing in Grammarly’s documentation that singles out the hard message. We designed Subtext around it: the apology, the boundary, the reply to something that stung. That is a claim about fit only; our tone checker for text messages page shows what it looks like.

Neither tool can predict how a specific person will react

Grammarly and Subtext both read tone from the words alone, so neither can predict how a specific person will react. No independent evaluation of Subtext’s tags, score or rewrites exists. Grammarly’s tone checker works from word choice, phrasing, punctuation and capitalisation (Writing Tone Detector and Tone Suggestions)⁸. Subtext’s safe-to-send score, from 5 to 100, is our own estimate of how likely a version is to land the way you meant it, a second reading rather than a measurement³.

Two apology papers suggest how much rewriting to accept from Grammarly or Subtext. Each is a single paper built on written scenarios, and neither tested real messages or either tool. Glikson and Asscher ran three scenario experiments on workplace apologies (AI-mediated apology in a multilingual work context: Implications for perceived authenticity and willingness to forgive)⁹. Knowing the sender had relied on AI tools lowered perceived authenticity and, through it, willingness to forgive. Limited use of one tool, translation or grammar correction alone, had no negative effect on authenticity. Fan, Liu and Pan ran a randomised experiment with 704 people reading apologies and boundary requests set in intimate relationships (Is It Still You? Attributing Authorship and Authenticity in AI-Assisted Romantic Communication)¹⁰. Heavier AI drafting reliably made a message feel less like the sender’s own. For apologies, a disclosed light tone rewrite raised authenticity and forgiveness, while a disclosed full AI draft slightly lowered both.

Treat Grammarly’s tone suggestions and Subtext’s versions as feedback on your own words, and be suspicious of any output that has replaced them. The full apology evidence is in our guide to apologising over text.

Subtext reads the whole thread; Grammarly’s AI Chat uses the active window

Subtext reads the whole exchange from pasted text, a screenshot or a voice note. It works out whose bubbles are whose in a screenshot and asks when it cannot tell; the App Store version history describes the same question for pasted text (Subtext: AI Writing Assistant on the App Store)¹¹. For a message you received, it summarises what the other person wants in plain words, lists up to five things that need an answer, and drafts a reply that picks up the thread. The trigger tags never run on the other person’s message, so it does not label what someone sent you as hostile or manipulative. More on reading the message you received before you reply.

Grammarly is not context-free. AI Chat in Grammarly for Windows and Mac uses “context from the currently active window”, and you can attach a different open window to guide it (AI Chat in Grammarly for Windows and Mac user guide)¹². What we found no documentation of, on 23 September 2026, is Grammarly reading a screenshot of a personal chat and drafting a reply from the thread.

Can either tool keep your voice?

Grammarly and Subtext approach your voice from opposite directions, and I found no test of either approach. Grammarly, on paid plans, detects a voice profile from your writing, one for documents and one for messages, and offers “rewrite in my voice” as a prompt⁵.

What the research does show is that the penalty for AI help depends on disclosure or suspicion. Zhu and Molnar, in a single paper of two online experiments with 1,301 US adults, found that explicit disclosure of AI use produced more negative impressions than confirmed human authorship, and that the penalty “disappeared or was significantly reduced under more realistic conditions” (Blissful (A)Ignorance: Despite the widespread adoption of AI in communication, people do not suspect AI use in realistic contexts)¹³. The study tested no particular tool, so the same caution applies to Grammarly and Subtext; the evidence is in does AI make your texts sound like a robot.

Subtext has no learned voice profile and no line-level accept-or-reject editor. It starts from your draft and reads how close you and the other person are from the tone of what you wrote. Each version shows how much of your wording it changed, so a drifted rewrite is visible. You can tap Warmer, Shorter, More casual, Add humor or Add confidence, or open Manual edit and change a word yourself before you copy. For everyday messages it does not interrupt; hand it a boundary, a refusal or a confrontation with no word on who it is for, and it asks two to four questions before drafting. Try Subtext in your browser

Platforms and pricing, checked 23 September 2026

Grammarly and Subtext run on different surfaces. Subtext is an iPhone, iPad and Android app and a web app at web.subtext.it for Safari, Chrome, Edge, Firefox, Opera and Brave, built for the phone first³. It has no keyboard, no browser extension and no offline mode, because the reading and rewriting happen on our servers. It comes in 17+ languages and answers in the one you write in; Grammarly lists correctness in more than twenty². Neither count says anything about quality.

On price, Grammarly has a free tier and Pro, Business and Enterprise tiers above it². Subtext gives you a few free analyses to start. After that it is a paid subscription with weekly, monthly and yearly plans, billed through the App Store or Google Play on your phone or through Stripe on the web, with the price shown in your currency before you subscribe³.

Privacy and two different data flows, checked 23 September 2026

Neither Grammarly nor Subtext is “more private” in a way I can defend; they move your words differently. Grammarly works where you type, so while you are actively using it, it reads what you write there, skipping sensitive fields such as passwords and payment details on a best-efforts basis (How We Protect Your Privacy)¹⁴. For individual Free, Premium and single-user Pro accounts, its Product Improvement and Training setting is on by default, with an opt-out in privacy settings; for Business, Enterprise and Education accounts bought through sales it is off by default, and multi-user Pro teams bought on the website start with it on, under an admin’s control (Product Improvement and Training Control)¹⁵. Its separate statement that third-party language-model providers may not train on user content is a different thing (Privacy and security FAQs)¹⁶.

Subtext sees only what you deliberately hand it, and for a screenshot that includes the other person’s words. Your messages go to the AI providers that read and write them and to our servers, so you can come back to a conversation; the privacy policy names every provider (Terms, Privacy and your account: Privacy Policy)¹⁷. If you use the optional web search, the search terms go to a search provider; you can turn it off in settings. Nothing you send is used to train an AI model, and it is encrypted on the way. Delete a conversation yourself and it is gone straight away, attachments included.

Which tool fits which task

The scenarios below map Grammarly and Subtext to tasks by fit alone.

Spelling and grammar as you type, in the apps you already use. Grammarly, which sits in the keyboard, the browser and Word.

Long documents, reports and brand-consistent writing at work. Grammarly. Style guides, single sign-on and audit logs are on its plans page².

Replying to a personal conversation or a voice note. We designed Subtext for that job; we found no Grammarly documentation of that workflow.

A deliberate second reading of a hard message before you send it. We built Subtext around that pause. Grammarly’s tone detector reads the draft where you type it; we found no documentation of it reading the conversation.

Not wanting a keyboard or extension that sees what you type. Subtext sees only what you hand it. If you keep Grammarly, check its training setting once.

An apology, in Grammarly or Subtext. Accept light edits of your own words; in the apology experiments above, heavier AI drafting made a message feel less like the sender’s own.

Plenty of people will use both, Grammarly for the working day and Subtext for the message still unsent at 11pm. The longer field guide is most tone checkers never check your tone.

Questions people ask

Subtext vs Grammarly for personal messages and tone checking: what is the difference? Grammarly is a writing assistant that works where you type and detects the tone of your own text. Subtext is an app you bring a message or a whole conversation to; it marks the words that could read wrong and offers three versions. Neither can predict one person’s reaction.

Is there something better than Grammarly for personal texts and emotional messages? I cannot show you “better”, because no independent study compares the two and none evaluates Subtext. Grammarly’s documentation centres on work writing; Subtext’s centres on the personal message you are stuck on. Try your hardest unsent message in both.

Is there something like Grammarly but focused on tone and emotional impact, not just spelling? Yes, and Grammarly is partly one, since its tone detector sits on top of its correctness checks. Subtext starts from tone. It flags the words in your draft that could land as harsh, cold or passive-aggressive and explains why. It does not sit in your keyboard or check as you type.

Is there something better than Grammarly for understanding how my message might land emotionally? Grammarly’s tone labels and Subtext’s safe-to-send score both read the words alone, and neither knows the person you are writing to. Within that limit, Subtext takes on this question by naming what a phrase could read as and offering three versions one tap apart.

Is Subtext a Grammarly alternative? Only for one job. If you want a grammar checker in every text box, keep Grammarly. If your hard messages are personal, Subtext reads a screenshot or voice note of a conversation and drafts a reply that picks up the thread, a job we found no Grammarly documentation for.

Sources

Every link above goes to the primary source, numbered in order of first appearance. Product facts were checked on 23 September 2026; features, plans and policies change, so confirm them before you rely on them.

1. Grammarly (Superhuman) Support. Grammarly’s product offerings. Checked 23 September 2026.
2. Superhuman. Superhuman Suite pricing and plans. Checked 23 September 2026.
3. Subtext (Anton Licht c/o Hidden Sea UG, Berlin). Subtext: the AI tone checker for personal messages, homepage and FAQ. Checked 23 September 2026.
4. Grammarly. Grammarly Rebrands Company as Superhuman, Introduces Superhuman Suite and Superhuman Go. Grammarly blog, 29 October 2025.
5. Grammarly (Superhuman) Support. Introducing voice features. Checked 23 September 2026.
6. Grammarly (Superhuman) Support. Reader Reactions user guide. Checked 23 September 2026.
7. Pollmann, M. M. H., Roos, C. A. (2025). “I get u”. People correctly interpret the tone of text messages and emails. Computers in Human Behavior Reports, 18, 100689.
8. Grammarly. Writing Tone Detector and Tone Suggestions. Checked 23 September 2026.
9. Glikson, E., Asscher, O. (2023). AI-mediated apology in a multilingual work context: Implications for perceived authenticity and willingness to forgive. Computers in Human Behavior, 140, 107592.
10. Fan, G., Liu, D., Pan, L. (2026). Is It Still You? Attributing Authorship and Authenticity in AI-Assisted Romantic Communication. Proceedings of the 2026 CHI Conference on Human Factors in Computing Systems.
11. Anton Licht. Subtext: AI Writing Assistant, version 1.3.54 (10 September 2026). Apple App Store, US listing. Checked 23 September 2026.
12. Grammarly (Superhuman) Support. AI Chat in Grammarly for Windows and Mac user guide. Checked 23 September 2026.
13. Zhu, J., Molnar, A. (2026). Blissful (A)Ignorance: Despite the widespread adoption of AI in communication, people do not suspect AI use in realistic contexts. Computers in Human Behavior, 180, 108929.
14. Grammarly. How We Protect Your Privacy. Checked 23 September 2026.
15. Grammarly (Superhuman) Support. Product Improvement and Training Control. Checked 23 September 2026.
16. Grammarly (Superhuman) Support. Privacy and security FAQs. Checked 23 September 2026.
17. Subtext (Anton Licht c/o Hidden Sea UG, Berlin). Terms, Privacy and your account: Privacy Policy, last updated 26 July 2026. Checked 23 September 2026.