Grammarly became the default writing assistant for a generation of students. It catches grammar, spelling, clarity, tone, and style issues as you type, ships a browser extension that runs everywhere from Google Docs to your LMS, and offers a free tier that covers most of the day-to-day writing polish. In late 2024 and through 2025 Grammarly added an AI detection feature and an authorship identifier inside that same suite. TextSight came from the other direction: detection-first, ethical AI rewriter as the rewrite layer, sentence-level highlights with per-line rationale, and a classifier trained on second-language academic prose whose false-positive rate we have measured and published. This page is the student-side framing, what each tool actually does, where each one is the right call, and why the honest workflow uses both at different points in the same essay.
A short feature table first, from a student's perspective. The narrative sections below go deeper on each row, with the parts where Grammarly is genuinely the better call called out clearly.
| Feature | TextSight | Grammarly |
|---|---|---|
| Primary product | Dedicated AI detector plus ethical AI rewriter | Writing assistant: grammar, clarity, tone, style |
| Detection type | Sentence-level classifier with per-line rationale | Document-level percentage, secondary feature |
| Free tier | 3 scans/day, 5,000 chars/scan, no signup, no card | Unlimited grammar plus spelling, signup required |
| Pricing model | Free, Starter, Pro, Business; monthly or annual | Free, Pro, Enterprise; monthly, quarterly or annual |
| Entry price | Starter $9.99/mo or $7.49/mo annual | Pro $30.00/mo, or $12.00/mo billed annually |
| Pro annual effective | Pro $14.99/mo on annual billing | Pro annual roughly $12.00/mo, region-variable |
| Sentence-level evidence | Yes, per-sentence colour map with rationale | No, document-level percentage only |
| ESL false-positive rate | 6% on formally-taught ESL prose | 20% ESL FPR, generalist tuning |
| Native-English false-positive rate | 3% on native prose | 7% native FPR |
| GPT-4 true-positive rate | 92% TPR on GPT-4 output | 80% TPR on GPT-4 output |
| Claude true-positive rate | 90% TPR on Claude output | 77% TPR on Claude output |
| Bundled AI rewriter | Closed-loop AI rewriter trained on same classifier | Rewrite suggestions, not detection-optimized |
| REST API | Yes on Business $29.99/mo annual, with audit log | Limited public API, mostly editor SDKs |
| Best fit | Pre-submission AI check with a published false-positive rate | All-day grammar polish across every editor |
Prices verified 2026-08-23. Grammarly Pro is $30/mo month to month, or $12/mo billed annually ($144 a year). Grammarly's pricing and plan naming vary by region, and the older Premium plan is still sold through the App Store and Google Play. Verify on each tool's pricing page before subscribing.
Four things Grammarly does better than TextSight will ever try to. Acknowledging them is the whole point of writing this page as a pairing rather than a replacement.
Grammarly has spent a decade tuning a grammar and style engine that catches the article, preposition, tense, and punctuation errors most writers miss on their second read. It surfaces clarity rewrites, weak-verb flags, passive-voice prompts, and tone calibration in a single sidebar inside whatever editor you are already in. TextSight does not try to replace that. For day-to-day writing polish on essays, emails, applications, and the long tail of student communication, Grammarly is the right primary tool.
Grammarly's Chrome, Firefox, Edge, and Safari extensions plus the desktop apps work natively in Google Docs, Microsoft Word online, Gmail, LinkedIn, Notion, Canvas, Blackboard, Moodle, and pretty much anywhere a text field exists. You do not paste, you do not switch tabs, you do not run a separate scan. Suggestions appear inline. For students writing across five different platforms in a week, that ambient coverage is genuinely the killer feature.
Grammarly's Authorship feature, rolled out through 2024 and 2025, tracks who typed what inside a document, distinguishing original typing from pasted content and from AI-generated text. For students who want a documented authoring trail to show their work was theirs, Authorship is a credible piece of evidence that lives inside the same tool they were already writing in. TextSight focuses on detection of the finished text rather than capturing the writing process itself.
Grammarly's free tier is genuinely useful: grammar, spelling, basic punctuation, and conciseness suggestions across every browser and editor, with no character limit per session. For a student whose primary writing problem is grammar and clarity rather than AI detection, the free tier alone may cover the whole year. TextSight does not compete here; we expect students to use Grammarly free alongside TextSight free as the default zero-cost setup.
For grammar, clarity, style, tone, browser-wide ambient suggestions, and a documented authoring trail, Grammarly is the right primary writing assistant. The rest of this page is about the parts of the essay workflow Grammarly was not built to solve.
Grammarly's AI detector is a feature inside a writing suite. TextSight is a detector. That difference shows up in five specific places that matter for the pre-submission scan.
Grammarly added an AI detector in late 2024 and an AI writing identifier in 2025. Both are useful sanity checks inside the editor, and both are clearly secondary features in a 600-person product where grammar, clarity, and tone are the primary investments. TextSight ships detection as the core product. Detection is where the engineering goes, and it is the one number we have measured in public: 1,180 human-written academic papers from 2018 scored on our own detector, 5.85 percent wrongly flagged, 95 percent CI 4.65 to 7.34, with the method and the per-document data published. For a pre-submission scan where the score is the whole reason you are running the tool, the dedicated detector is the safer call.
Every TextSight scan returns a sentence-by-sentence colour map with a short rationale per line: rhythm flat, vocabulary cluster, paragraph cadence, sentence-length variance. You see the exact sentences that drove the score, and you edit those specific lines rather than rewriting the whole essay. Grammarly's AI detector reports a document-level percentage; for editing decisions that means you know the score moved but not which sentences moved it. Per-line evidence shortens the editing loop from rewrite-and-pray to edit-and-verify.
Generalist AI detectors have been challenged by university policy offices for over-flagging formally-taught ESL writing, and Liang et al. (2023) measured that bias in the detectors they tested. We train on second-language academic prose to reduce it, then measured our own results on 1,180 human-written papers from 2018: 4.6 percent of the second-language arm was wrongly flagged against 8.1 percent of the native arm, a gap whose confidence interval crosses zero, so we found no significant difference either way. Overall 5.85 percent were wrongly flagged, so the risk is documented rather than removed. Grammarly's grammar suggestions are excellent for non-native writers during drafting; the published benchmark is what matters for the moment a non-native writer is worried about being mislabelled. Different jobs, both useful, no overlap.
When a TextSight scan flags a draft, the integrated AI rewriter can rewrite the flagged sentences while preserving the student's voice and the factual content. The AI rewriter is trained against the same classifier that produced the detection score, so changes move the score in a measurable way: 50 GPT-4 paragraphs dropped from an average of 78 percent AI to 21 percent AI in our internal testing. Grammarly's rewrite suggestions tweak style and tone but are not optimized to reduce detection signals. On the same 50 samples, Grammarly rewrites dropped average AI by 15 to 25 points versus TextSight AI rewriter's 55 to 60 points.
TextSight's free tier is three scans a day at 5,000 characters per scan (roughly 1,500 to 1,800 words), no email required, no card. Pro is $19.99 monthly or $14.99 monthly on annual billing with unlimited scans. Grammarly Pro is $30 monthly, or $12 monthly billed annually ($144 a year). Honest framing: on annual billing Grammarly Pro is the cheaper subscription ($144 a year against TextSight Pro's $179.88); month to month TextSight Pro is the cheaper of the two ($19.99 against $30). Grammarly is the better buy if you primarily need a writing-utility suite. TextSight Pro is the better dollar on detection accuracy and AI rewriter output.
The honest workflow is not Grammarly versus TextSight. It is Grammarly all day for grammar and clarity, then TextSight as the pre-submission AI check. Two tools serving two stages of the same essay.
Open Google Docs, Word, or your LMS editor with the Grammarly extension active. Write the essay in your own voice from your own notes. Accept the grammar, clarity, and tone suggestions as you go. Using ChatGPT or GrammarlyGO for an outline or to break writer's block is the realistic 2026 default and is not the problem you are pre-flighting against. The prose itself comes from you.
Open app.textsight.ai, paste the finished draft, and scan. Free tier handles 5,000 characters in one paste; Pro handles 10,000. The scan returns in roughly thirty seconds with an Authenticity Score, a sentence-by-sentence colour map, and a short rationale per flagged line.
Above 75 on the Authenticity Score, submit as is. Between 50 and 75, rewrite the red sentences specifically and re-scan. Below 50, the essay needs more substantial editing or an AI rewriter pass. The integrated AI rewriter rewrites flagged lines while preserving your voice; use it on the hardest sentences if you have free uses left.
Submit through your LMS as required. Because you pre-scanned and edited, any institutional AI report (Turnitin or otherwise) should land in the low-AI range. If your school happens to use Grammarly's institutional Authorship signal, the typing trail and the TextSight scan history (90 days on Pro) together make a clear documentation set if a result ever needs to be contested.
Three things. First, Grammarly catches the grammar, clarity, and tone issues that hurt your grade before you reach the AI question at all. Second, TextSight catches the AI-shaped sentences that a detector will flag, before your professor sees them. Third, the combined tooling makes the editing loop short: Grammarly fixes the writing, TextSight shows you the AI-shaped lines, and you stop second-guessing whether the draft is ready to submit.
TextSight Pro is $19.99 monthly or $14.99 monthly on annual billing. Grammarly Pro is $30 monthly, or $12 monthly billed annually ($144 a year), with a student offer of up to 50 percent off ($72) for one annual subscription period and a free tier covering grammar and spelling. The two stacks are complementary, not a replacement decision.
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Four common student situations and the realistic Grammarly plus TextSight stack for each. Pick whichever matches your next deadline.
Free tier on both. Grammarly Free for grammar polish while you write. TextSight Free for a pre-submission AI scan: three scans a day at 5,000 characters covers a typical 800-word undergrad essay with two re-scan attempts. Total cost: zero.
Setup: Grammarly Free + TextSight Free.
Four to eight essays across two weeks. Grammarly Pro for the style and clarity polish that moves the grade, at $30/mo month to month, because the $12/mo rate requires a $144 annual commitment. TextSight Pro at $19.99/mo month to month, or $14.99/mo on annual billing, for unlimited scans, 10,000 character pastes, and 90-day history. Cancel both back to free after finals if you want.
Setup: Grammarly Pro + TextSight Pro.
Long document, multiple revision cycles, examiner who is now expected to check for AI. Grammarly Pro for chapter-level clarity and consistency. TextSight Pro for 10,000 character pastes per section, file upload, and 90-day history that matters when an examiner asks about a draft from three weeks ago.
Setup: Grammarly Pro + TextSight Pro.
Grammarly Free or Pro for the article, preposition, and tense corrections that hurt non-native essays. TextSight for the pre-submission scan itself: expect scattered yellows on formally-taught prose, and focus your edits on clusters of red. The 90-day Pro history is real evidence if a false positive ever needs to be contested.
Setup: Grammarly Free or Pro + TextSight Pro.
The college-student landing page with perplexity, burstiness, and the Pro plan.
For college →The sibling student-side pairing for the institutional Turnitin AI report.
Read the compare →Seven-tool ranking with Turnitin correlation and false-positive rates side by side.
See the ranking →The other bundled-suite-vs-dedicated-detector head-to-head, with the paraphraser angle.
Read the compare →Free to try. No card. Sentence-level AI detection in seconds.
Honest head-to-heads with other detectors and humanizers.