21st Agents SDK vs Persona.js: Pricing and Ratings Compared (2026)
Entry prices and free plans as read on each vendor's pricing page, and user ratings as published on review sites, for 21st Agents SDK and Persona.js side by side. This page compares data; it is not a hands-on review.
On the data: On the data below the two are close or not directly comparable, so we do not name a winner for this pair.
Short on time? Here's the quick answer
Based on published vendor pricing and features and on public review data, here's who should pick what:
21st Agents SDK
The fastest way to integrate AI agents with built-in UI and essential features into your applications.
Best for you if:
- • You want accelerates AI agent integration
Persona.js
Build AI agent experiences directly into your web app
Best for you if:
- • You want a fully free tool (21st Agents SDK requires payment)
| At a Glance | 21st Agents SDK | Persona.js |
|---|---|---|
Starts at | Free plan, paid from $6/mo, billed monthly Builder plan | Free 100% free |
Category | AI Agents Developer Tools | AI Agents Developer Tools |
Rating | n/a | n/a |
Free plan | Yes | Yes |
Watch out for | These $ are billed yearly. The page says save 25% vs quarterly. | n/a |
Choose 21st Agents SDK or Persona.js?
Choose 21st Agents SDK if
- You want accelerates AI agent integration
- You want provides essential features out-of-the-box
Choose Persona.js if
- You want a fully free tool (21st Agents SDK requires payment)
- You want pure VanillaJS, ensuring broad compatibility and lightweight footprint
- You want offers flexible UI layouts to suit different application needs
In-Depth Analysis
21st Agents SDK
The fastest way to integrate AI agents with built-in UI and essential features into your applications.
21st.dev publishes yearly list prices: Builder $6/month, Builder + AI $15/month, Team $7.50/seat/month (2–50 seats).
Watch out
These $ are billed yearly. The page says save 25% vs quarterly.
Strengths
- Pro: Accelerates AI agent integration
- Pro: Provides essential features out-of-the-box
- Pro: Compatible with popular web technologies
- Pro: Handles complex aspects like memory and tool use
Key features
Persona.js
Build AI agent experiences directly into your web app
Strengths
- Pro: Pure VanillaJS, ensuring broad compatibility and lightweight footprint.
- Pro: Offers flexible UI layouts to suit different application needs.
- Pro: Strong styling capabilities for seamless brand integration.
- Pro: Designed for isolation, preventing style conflicts with host applications.
- Pro: Supports various backend integrations, including custom SSE setups.
Weaknesses
- Con: Requires some development effort to integrate and configure with existing backends.
- Con: Relies on WebMCP for agent actions, which might require understanding a new paradigm for some developers.
Key features
Plans and prices: 21st Agents SDK vs Persona.js
| Tool | Plans and prices | Source |
|---|---|---|
| 21st Agents SDK |
| 21st.dev/pricing read Oct 23, 2026 |
| Persona.js | No plan prices on file | persona-chat.dev |
Prices as read on each vendor's own pricing page on the date shown. Plans are listed per tool and are not matched against the other tool's plans: a plan name or price in one column says nothing about the same row in the other. Details on 21st Agents SDK pricing and Persona.js pricing.
Key Takeaways
21st Agents SDK
- Choose if you want the fastest way to integrate AI agents with built-in UI and essential features into your applications
Persona.js
- Choose if you want build AI agent experiences directly into your web app
What the data shows
On the data below the two are close or not directly comparable, so we do not name a winner for this pair.
- 21st Agents SDK starts at $6/mo, billed monthly; Persona.js has no public paid plan price on file.
- Both have a free plan.
Criteria: user rating (only above 20 reviews on both sides, gap of 0.2 or more), entry price (only on the same billing basis), free plan. How we rate
Frequently Asked Questions
How do 21st Agents SDK and Persona.js compare in 2026?
On the data below the two are close or not directly comparable, so we do not name a winner for this pair. 21st Agents SDK starts at $6/mo, billed monthly; Persona.js has no public paid plan price on file. Both have a free plan.
What are 21st Agents SDK and Persona.js used for?
21st Agents SDK: The fastest way to integrate AI agents with built-in UI and essential features into your applications. Persona.js: Build AI agent experiences directly into your web app.
What does 21st Agents SDK cost vs Persona.js?
21st Agents SDK's cheapest paid plan is Builder at $6/mo, billed monthly; it also has a free plan. Persona.js is free. Prices read on the vendors' pricing pages, latest check Oct 23, 2026.
What's the main difference between 21st Agents SDK and Persona.js?
21st Agents SDK's main strength: accelerates AI agent integration. Persona.js's main strength: pure VanillaJS, ensuring broad compatibility and lightweight footprint.