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Both tools schedule Substack Notes and can run from Claude or ChatGPT. SubflowAI is a low-cost Chrome extension with batch scheduling and a publication KPI dashboard. WriteStack publishes through Sync and your own Chrome extension, and adds per-Note subscriber analytics and engagement tools (Standard plan and up). Here's the full picture.
WriteStack and SubflowAI both let you schedule Substack Notes, generate Notes with AI, and drive that work from Claude or ChatGPT. WriteStack publishes through its own Sync and the Chrome extension in your browser session. SubflowAI's main app runs through your own Substack session with no cookie handed over, and its Notes are scheduled on Substack's servers. Its BYOK Claude setup is the exception: it asks you to paste your substack.sid cookie. This page breaks down everything else too.
SubflowAI suits writers who want a low-cost Chrome extension with batch scheduling and a publication KPI dashboard. WriteStack suits writers who want per-Note subscriber stats and the Activity Center (Standard plan and up), a Following feed and cross-posting through Buffer.
Competitor details and prices checked 20 Oct 2026 from their public pages.
SubflowAI ships a visual calendar, batch scheduling of about 30 Notes, a publication KPI dashboard (ARR, retention, progress toward Bestseller), a subscriber export, and a set of named Note formats. The price is low: $9.97 a month, or $99.97 for five years with Claude and ChatGPT access included.
The one caution is its Claude and ChatGPT connector. Relay mode keeps the cookie in Chrome. BYOK mode asks you to paste your substack.sid into your MCP client config, and SubflowAI's own page warns that this “may violate Substack's Terms of Service.”
Scroll through the table. Column headers stay pinned so you always know which product is which.
| Feature | WriteStackToS-safe | SubflowAI⚠ BYOK cookie risk |
|---|---|---|
| ⚠ Account Safety | ||
| Publishes through Sync and your own Chrome extension | Yes | Chrome extension; Notes scheduled on Substack's servers |
| Main app works without handing over your Substack cookie | Yes | YesSubflowAI: "No password, no cookie, and none of your content on our servers." |
| Claude / ChatGPT setup without pasting a cookie | Yes | Relay mode onlyBYOK mode pastes your substack.sid into the MCP config; SubflowAI says this "may violate Substack's Terms of Service" |
| Scheduling | ||
| Schedule Substack Notes | Yes | Yes |
| Visual posting calendar | Yes | Yes |
| Heatmap of posting habits | Yes | Not listed |
| Bulk-schedule Notes | Yes (queue holds 20, 100 or unlimited Notes by plan) | Yes (batch about 30 Notes) |
| Personalized optimal time suggestions | Yes | Not listed |
| Configurable time slots | Yes | Yes |
| Tag-based queue lanes | Yes | Not listed |
| Auto-restack after publish | Yes | Not listed |
| AI & Content Creation | ||
| AI Note generation in your voice | Yes | Yes |
| Generate Notes from articles & files | Yes | Yes |
| Voice learned from your published writing | Yes | Brand Voice settings |
| Tone-matched rewrites & variations | Yes | Yes |
| AI chat with your Substack context | Yes | Yes |
| Built-in web research | Yes | Not listed |
| Named viral Note formats | No | Yes |
| Analytics | ||
| Notes performance dashboard | Standard plan and up | Yes |
| Subscriber conversion tracking per Note | Standard plan and up | Per-article signups |
| Format & timing breakdown | Standard plan and up | Not listed |
| Growth correlation graphs | Standard plan and up | Not listed |
| Publication KPIs (ARR, retention, Bestseller progress) | No | Yes |
| Engagement & Community | ||
| Unified Activity Center (notifications) | Standard plan and up | Not listed |
| Reply inbox | Standard plan and up | Yes |
| Keyboard shortcuts for replies | Standard plan and up | Not listed |
| Auto-like on reply | Standard plan and up | Not listed |
| Search millions of Notes in your niche | Enterprise plan | Not listed |
| Follow & curate a creator list | Yes (10, 20 or 80 creators by plan) | Not listed |
| Personalized Following feed | Yes | Not listed |
| Engage directly from your Following feed | Yes | Not listed |
| Subscriber CRM export | No | Yes |
| Cross-platform posting | ||
| Cross-platform posting | Standard plan and up (via Buffer) | Not listed |
| Articles | ||
| Plan, generate, and schedule articles on Substack | Yes | Not listed |
| Claude & ChatGPT | ||
| Drive scheduling from Claude or ChatGPT | Standard plan and up | YesConnect add-on ($30) or Premium |
| Power Users & Teams | ||
| Multiple publications / ghostwriter mode | Yes | Not listed |
| Works on any browser / device for planning | Yes | Yes |
| Chrome extension for publishing | Yes | Yes |
| Pricing (checked 20 Oct 2026) | ||
| Monthly price | $23.99, $32.99 or $99.99 a month (Hobbyist, Standard, Enterprise), or $19.99, $24.99 or $79.99 a month billed yearly | Pro $9.97 a month; or one-time Pro $69.97 or Premium $99.97 for 5 years (Premium includes Connect) |
| Free plan or trial | 7-day free trial on every plan, no free plan | 5-day free trial (500 AI generations); 14-day money-back guarantee |
Prices checked 20 Oct 2026. "Not listed" means we could not find the feature on the competitor's public pages that day.
Ready to see it in action?
Start your free 7-day trial →SubflowAI's main app says: “No password, no cookie, and none of your content on our servers.” Its Claude and ChatGPT connector has a second mode, BYOK, where “you paste your own substack.sid into your MCP client config.” SubflowAI's own disclaimer says this “may violate Substack's Terms of Service.” The rule it points to:
“You also agree that you will not contribute any Post or otherwise use Substack in a manner that:
...
- • Jeopardizes the security of your Substack account or anyone else's (such as allowing someone else to log into Substack as you, or sharing your account or password with someone)
...”
If you use SubflowAI, pick relay mode. Pasting substack.sid into a connector hands over your login, because the cookie is the session.
WriteStack publishes through Sync and the Chrome extension in your own browser. We never ask for your password or session cookie, and your credentials never leave your browser.
Sync + extension publishing
Notes publish from your browser session via Sync, with no cookie harvest on our servers
No credential exposure
Your session cookies stay in your browser, always
No password handover
WriteStack never asks for your Substack password or session cookie
Beyond account safety, these are the features that make the biggest difference for writers serious about Substack growth.
WriteStack publishes through Sync and the Chrome extension in your own browser session, and Sync runs automatically. No WriteStack setup asks you to paste your Substack session cookie. SubflowAI's main app says the same. Its BYOK Claude setup asks you to paste the cookie.
SubflowAI shows publication-level numbers (subscribers, ARR, open rate, a path to Bestseller) and per-article signups. On the Standard plan and up, WriteStack shows each Note's impressions, clicks, restacks, and free and paid subscribers, so you know what to write next.
WriteStack drafts from your published writing, your style, and your Substack context. SubflowAI uses Brand Voice settings plus a set of named formats.
The Activity Center (Standard plan and up) replaces Substack's chaotic notification feed. Reply with keyboard shortcuts. Auto-like on reply. SubflowAI has a reply inbox.
Build a curated list of creators you want to engage with and read their Notes in a single feed, directly inside WriteStack. We could not find a similar feature on SubflowAI's site.
On the Standard plan and up, connect Buffer and cross-post to X, LinkedIn, Threads, and more, including different text per channel. SubflowAI stays inside Substack.
Ready to see it in action?
Get started free →Real writers. Real publications. You can look them up.
"My new subscribers growth rate doubled ever since. It saves me hours of posting manually."
Yana G.Y.
Unplugged by Yana G.Y.
"The Notes analytics alone are a game-changer — actual data showing which posts convert to subscribers."
Dino | The Art of Purpose
masterclass247.com
Common questions about WriteStack and SubflowAI
See how WriteStack stacks up against other tools
SubflowAI is a low-cost Chrome extension that schedules Notes and talks to Claude. Use its relay mode, because its BYOK mode asks for your Substack cookie. WriteStack schedules through Sync and your own Chrome extension, shows which Notes convert, and runs from Claude (Standard plan and up), with a Following feed and Buffer cross-posting.
Schedule Notes with Sync + the Chrome extension, track what converts, follow creators you care about, and generate content in your voice. Free for 7 days.