AI Writer: 4 Modes to Draft Anything from Any App
Arc's AI Writer lets you rewrite text, fix grammar, reply to conversations, and create posts — all from a floating panel in any app. Here's how to use each mode.
You’re staring at a text field. Maybe it’s a reply to a client email, a comment on a social post, or a message in a group chat. You know what you want to say, but getting the words right takes time.
Arc’s AI Writer takes that friction away. It opens as a floating panel right on top of whatever app you’re in, reads the context, and drafts text for you — in four distinct modes.
The Four Modes
1. Rewrite
Select or type text in any input field, then tap AI Writer. Rewrite takes your existing text and rephrases it — making it clearer, more professional, or more concise depending on the tone you choose.
When to use it: You’ve written a draft but it doesn’t sound right. Rewrite polishes it without changing the meaning.
2. Fix Grammar
Fix Grammar scans your text for grammatical errors, awkward phrasing, and typos, then corrects them while preserving your original voice and intent.
When to use it: You’ve typed something quickly and want to make sure it reads well before sending. Especially useful for non-native speakers or quick mobile typing.
3. Reply
Reply mode is context-aware. Arc reads the conversation thread visible on your screen — a chat, email, or comment thread — and drafts a reply that matches the context and tone of the conversation.
When to use it: You’re replying to a message and want a contextually appropriate response without typing from scratch. Arc understands the thread, not just the last message.
4. Create Post
Create Post generates original content based on a prompt or the content on your screen. Write social media posts, product descriptions, or announcements.
When to use it: You need to create something new — a LinkedIn post about an article you’re reading, a tweet summarizing a report, or a product review.
Tone and Length Options
Each mode lets you adjust two parameters:
- Tone — Choose from options like professional, casual, friendly, or formal to match the context.
- Length — Control whether the output is short and punchy or detailed and thorough.
These options mean you can use the same mode for very different situations. A “Rewrite” in professional tone reads differently from one in casual tone.
How Info Vault Makes It Personal
Here’s where AI Writer gets really powerful. If you’ve set up your Info Vault (Settings → My Info Vault), AI Writer automatically pulls in your personal details when they’re relevant.
For example, if your vault has an “About me” item, a “My role” item, and “Writing preferences”, AI Writer will use these to:
- Sign off with your actual name and title
- Match your preferred writing style
- Reference your role when drafting professional responses
You define the vault items — there are no fixed fields. Add whatever personal context you find useful.
How to Use AI Writer
- Focus a text field in any app — email, messaging, social media, notes
- Swipe to open the Arc sidebar
- Tap AI Writer
- Arc detects the focused field and extracts its current text (and conversation context for Reply mode)
- Choose your mode, tone, and length
- Tap Generate
- Review the draft, then Insert it directly into the field or Copy to clipboard
The entire flow happens in a floating panel on top of the app you’re in. No switching apps, no copy-pasting between screens.
Real-World Examples
Replying to a Client Email
You receive a detailed project email. Focus the reply field, open AI Writer, choose Reply with a professional tone. Arc reads the email thread and drafts a response that addresses each point.
Fixing a Quick Message
You’ve typed a message quickly on your phone. Select it, tap AI Writer, choose Fix Grammar. Typos and awkward phrasing are corrected instantly.
Creating a Social Post
You’re reading an interesting article in Chrome. Open AI Writer, choose Create Post with a casual tone. Arc summarizes the article into a shareable social media post.
Rewriting for a Different Audience
You’ve drafted a technical explanation. Select it, tap AI Writer, choose Rewrite with a friendly tone and short length. Arc rephrases it for a non-technical audience.
AI Writer works best when you pair it with Info Vault for personalization and use the right mode for the situation. Once you get the hang of the four modes, drafting text on your phone becomes as fast as it is on a desktop — maybe faster.