AI Grammar Checker Keyboard for Android

Never send an embarrassing typo again. Get on-demand grammar correction, spelling fixes, and tone alignment inside any app on your phone.

Last updated: July 20, 2026

Why Use an AI Grammar Keyboard?

Grammar correction apps usually force you to type in a separate document editor, copy the text, and paste it back. Synapse replaces Gboard or SwiftKey to provide on-demand grammar correction directly where you write, saving time and keeping you inside the conversation.

It's on-demand, not as-you-type: Synapse doesn't underline mistakes while you write — you ask for a fix when you're ready to send. If you want passive red-underline correction as you type, Grammarly's keyboard does that better. Synapse is for people who'd rather draft freely and clean up in one action — and who also want translation, tone rewriting, and custom prompts in the same keyboard.

On-Demand Grammar Fix

Select your text, tap the Synapse icon, tap Fix Grammar — the corrected version replaces your draft in the same chat box. No copy-pasting to a separate editor.

Tone Rewriting

Need to make a casual WhatsApp text sound professional? Shift your tone dynamically with AI.

See It In Action

their going to the store tommorow→They're going to the store tomorrow

i would like to inquire about the position→I'd like to inquire about the position

me and my team we are working on project→My team and I are working on the project

can you send me the report as soon as possible→Could you send me the report at your earliest convenience?

Rough draft message with grammar mistakes before running Synapse grammar fix

Same message after Synapse grammar fix — polished and professional

Works In Every App

Unlike browser extensions, Synapse works system-wide. Whether you're in WhatsApp, Gmail, Slack, Twitter/X, or any other Android app — grammar help is always a few taps away.

WhatsAppGmailInstagramSlackTwitter/XUpwork

See all features → Full Synapse Feature List · Compare with competitors

Grammar Checker Keyboard FAQ

Is Synapse a free grammar checker keyboard?

Yes — the keyboard itself is free to download with 20,000 free energy credits on signup. Grammar fixes and other AI actions spend a small number of credits per request, and you top up pay-as-you-go starting at $5. There is no subscription.

Does Synapse underline grammar mistakes as I type?

No. Synapse is on-demand: you select your text, tap Fix Grammar, and the corrected version replaces your draft. If you want passive red-underline correction as you type, Grammarly's keyboard does that better. Synapse is for drafting freely and cleaning up in one action.

Which apps does the grammar checker work in?

Every Android app where you can type: WhatsApp, Gmail, Instagram, Slack, Twitter/X, Upwork, and more. Because it's a system keyboard, grammar help is available anywhere text input is.

Does it translate or rewrite tone too?

Yes. Beyond grammar, Synapse can translate messages to many languages and rewrite tone (casual to professional) using the same select-and-tap workflow.

Do I need to copy-paste my text to check grammar?

No. That's the point — grammar correction happens right in the app you're typing in, so there's no copy-pasting to a separate editor or chatbot.

Get Free AI Grammar Checker Keyboard