Rithere vs Grammarly vs Copilot

The same six jobs done three ways, and what happens to your text in Word compared with a plain text box. Written for everyday users and reviewers alike.

5 min read Checked against official sources, October 2026

Written by Rithere's developer. Grammarly and Copilot steps come from their own documentation, not lab tests. The small numbers link to each source, checked October 2026.

Three kinds of help

Grammarly watches as you type and suggests fixes.1 Copilot is strongest inside Word and Outlook,2,3 and on Copilot+ PCs (newer PCs with a built-in AI chip) its Click to Do adds rewrite presets anywhere on screen.4 Rithere waits until you highlight text and press a key, then runs your saved instruction.5

Rithere for…

  • your own instructions, each on a key
  • one shortcut in almost every app
  • explanations that leave text alone

Grammarly for…

  • catching mistakes as you type
  • Windows, Mac, browsers, phones
  • plagiarism and AI-writing checks

Copilot for…

  • deep work in Word and Outlook
  • on-device AI on Copilot+ PCs
  • teams on Microsoft 365

Six tasks, three ways

What you do, step by step, from text you've already written.

1. Fix grammar in an email

Outlook

Grammarly
  1. Type as usual
  2. Click each underline

This is what it's for.1

Copilot
  1. Open Coaching by Copilot
  2. Review its tips

Tips on tone and clarity, not spelling. Needs Microsoft 365.6,7

Rithere
  1. Highlight the draft
  2. Press Proofread

Fixed in place, but only when you ask.5

2. Turn rough notes into an email

Outlook or Gmail

Grammarly
  1. Highlight
  2. Click the blue bar
  3. Type the instruction
  4. Accept

Uses one of 100 free prompts a month.1,8

Copilot
  1. Draft with Copilot
  2. Describe the email
  3. Keep it

In Outlook.3

Rithere
  1. Highlight
  2. Press Raw thought to Email

Comes with the app. Same key in both.

3. Make a chat message friendlier

Slack or Teams

Grammarly
  1. Highlight
  2. Click the blue bar
  3. Pick or type a rewrite
  4. Accept

Works across many desktop apps.9

Copilot
  1. Click to Do: Windows key + click
  2. Select 10+ words
  3. Rewrite (Casual)
  4. Copy the result

Copilot+ PCs only.4

Rithere
  1. Highlight
  2. Press your "friendlier" key

A prompt you write once.5

4. Explain a clause without changing it

A PDF or document

Grammarly
  1. Open AI Chat
  2. Ask about the clause

Answer in a side panel.10

Copilot
  1. Windows key + click, select
  2. Ask Copilot
  3. Read it in the Copilot app

Copilot+ PCs; not offered in the EU/EEA.4

Rithere
  1. Highlight
  2. Press Explain Simply

Answer beside your cursor.11

5. Summarise a long passage

Anywhere

Grammarly
  1. Highlight
  2. Open the sidebar or AI Chat
  3. Ask for a summary

Summaries are built in.10

Copilot
  1. Windows key + click, select
  2. Summarize

Built in on Copilot+ PCs.4

Rithere
  1. Add "Summarise this" from the app's gallery, once
  2. Highlight, press its key

Not a default prompt.

6. Apply your team's style, many times a day

Anywhere

Grammarly
  1. Save the style as instructions for its AI
  2. Accept suggestions as they come

Needs Superhuman Go turned on. No shortcut runs it.12,13

Copilot
  1. Select text in Word
  2. Describe the style each time
  3. Replace

Click to Do presets can't hold a style.4

Rithere
  1. Write the style into a prompt, once
  2. Highlight, press its key

Syncs to your other PCs.14

At a glance

Feature Rithere Grammarly Copilot
Suggestions as you type No Yes1 OutlookTone tips, when asked.6
AI rewrite in any app YesAny PC.5 YesVia the sidebar.1 Copilot+ PCsThree presets.4
Your prompt on its own key Yes No13 No4
Built into Word Via selection Desktop appOffice add-in retiring.15 Yes2
Plagiarism checks No Pro8 Not in CopilotWord has a separate Similarity check.16
Platforms Windows17 Everywhere8 Everywhere18
Cost of AI rewriting Free today17 Capped freePro $12/mo yearly.8 VariesOffice from $9.99/mo.18

Rithere in Word vs a plain text box

Rithere has no special Word mode. What matters is whether the text you highlighted has formatting in it.

Word, with formatting
Launch plan
The launch date moves to 14 March, and the plan stays as agreed: sign-off by Friday.
Bold, italics, links and headings stay.19 The result lands in one go. Check bullet lists afterwards.
Notepad, a web form, a chat box
The launch date moves to 14 March, and the plan stays as agreed: sign-off by Friday.
Plain text in, plain text out. You watch it appear as it's written.
  • Your clipboard comes back. Rithere saves it before a run and puts your copied text back after.19
  • Want to check first? Turn on preview before replace and nothing changes until you accept.14
  • Asking, not changing? Ask and AI Chat never write into your document.11,20
  • Tables lose their formatting: a selection with a table comes back as plain text.
For the technically curious
  • Rithere first reads the selection through Windows UI Automation, with no keystrokes; a selection with mixed formatting also gets one Ctrl + C to read that formatting. Where that can't answer (often browsers and Electron apps like Slack and VS Code), it falls back to a simulated Ctrl + C.19
  • Plain or evenly styled text is pasted in small batches as it streams. A selection with mixed formatting is sent with that formatting described, and the finished result is pasted once as formatted text.19 Word copies bullet and numbered lists in its own format, so those may not carry over.
  • Results are pasted, not typed. If a paste can't land (a read-only field), the result is left on your clipboard with a message.19
  • In recognised terminals Rithere never sends Ctrl + C (it would stop the running program); if it can't read the selection there, it says so. Apps running as administrator block it, and it tells you.19
  • For about a minute after a replacement, Alt + Z puts your original back on the clipboard; select the new text and press Ctrl + V.21,19

A ten-minute test for reviewers

Our take

They don't really compete for the same moment. Grammarly is best while you type. Copilot is best inside Word and Outlook with Microsoft 365. Rithere is best right after you've written something and want it changed, in whatever app you're in, with an instruction you saved. If that moment comes up a lot, it's worth the free download.

FAQ

Mostly. Bold, italics, underline, links and headings stay, as long as "Keep the formatting" is on, which it is by default.19 Check bullet lists after a rewrite, and note that a selection with a table comes back as plain text.

Not according to their documentation. Grammarly's shortcuts open its assistant and sidebar,13 and Click to Do opens with Windows key plus click, with fixed actions.4

Partly. It never presses Ctrl + C in a recognised terminal, because that would stop the running program. If it can't read the selection, it tells you and points you to AI Chat.19

Sources

Official pages, accessed 16 October 2026.

  1. Grammarly for Windows and Mac user guide
  2. Edit content and rewrite with Copilot in Word
  3. Draft an email with Copilot in Outlook
  4. Click to Do, Microsoft Support
  5. Rithere Prompts
  6. Get email coaching with Copilot in Outlook
  7. Copilot in Microsoft 365 subscriptions, FAQ
  8. Grammarly plans
  9. Grammarly with other apps
  10. AI Chat in Grammarly for Windows and Mac
  11. Rithere Ask
  12. Customize the Grammarly agent
  13. Grammarly keyboard shortcuts
  14. Rithere features
  15. Grammarly for Microsoft Office is being retired
  16. Check your document for similarity, Word
  17. Rithere FAQ
  18. Copilot pricing for individuals
  19. Rithere changelog
  20. Rithere AI Chat
  21. Where your text goes (Rithere)
  22. Rithere Right Click Menu

More comparisons

VS

Rithere vs Grammarly

Grammar as you type, against AI on a hotkey.

Read it
VS

Rithere vs Microsoft Copilot

Do you still need a separate app if you live in Office?

Read it

Which AI writing tool fits you?

Matched to the kind of work you do.

Read the guide

Run the test yourself.

Rithere is free for Windows. Install it, sign in with Google, and try the checks above in Word and Notepad.

Download Rithere Setup guide