Flexible bundles,
plus checkout offers.
Fast Bundle is a top-rated app for mix-and-match and build-your-own bundles. CheckoutOS covers bundles with cart transforms and adds checkout, post-purchase and thank-you page offers, rewards and checkout chat.$99/month. No sales-based tiers.
Self-serve software or help with setup and migration.
Side by side
See exactly what you get with each one.
Who each one is best for. Choose Fast Bundle if you need very flexible mix-and-match or build-your-own bundles, including in Shopify POS. Choose CheckoutOS if you want checkout offers, post-purchase upsells, bundles, checkout blocks and cart rules from one app for $99 a month, with no per-order fees.
Checked October 16, 2026. Fast Bundle facts come from the Fast Bundle App Store listing. “Not listed” means those pages didn’t name the feature when we checked, not that Fast Bundle can’t do it.
| Feature | Fast Bundle | Chargezen |
|---|---|---|
| Bundles Mix-and-match, fixed, BOGO and build-your-own | Included | Included |
| Cart upsells Offers in the cart drawer | Included | Included |
| A/B testing Test different offers | Included | Included |
| Offer a subscription Subscription upgrades | With Appstle and Seal | With Chargezen Subscriptions |
| Post-purchase upsells One-click offers after checkout | Not listed | Included |
| Thank you page offers Offers on the confirmation page | Not listed | Included |
| Rewards at checkout Show points as customers buy | Not listed | Included |
| Pricing by bundle sales Price rises with bundle sales | Included | No, $99/month |
Fast Bundle
- Bundles
- Included
- Cart upsells
- Included
- A/B testing
- Included
- Offer a subscription
- With Appstle and Seal
- Post-purchase upsells
- Not listed
- Thank you page offers
- Not listed
- Rewards at checkout
- Not listed
- Pricing by bundle sales
- Included
Chargezen
- Bundles
- Included
- Cart upsells
- Included
- A/B testing
- Included
- Offer a subscription
- With Chargezen Subscriptions
- Post-purchase upsells
- Included
- Thank you page offers
- Included
- Rewards at checkout
- Included
- Pricing by bundle sales
- No, $99/month
What you’d really pay
Fast Bundle prices by monthly bundle sales. CheckoutOS is one monthly price.
Fast Bundle
- Up to $1,000/mo bundle sales
- $19/mo
- Up to $3,000/mo
- $49/mo
- Up to $10,000/mo
- $139/mo
- Auto Bundle Detection
- +$49/mo
Estimated Annual Cost
Depends on bundle sales
Yearly plans are $180, $468 and $1,380. Free on development stores. Fast Bundle App Store listing, checked October 16, 2026.
Chargezen
- CheckoutOS
- $99/mo
- Per-order fee
- $0
- Share of upsell revenue
- $0
- Sales-based tiers
- None
Annual Cost
$1,188/year
CheckoutOS is $99/month, billed monthly, with no per-order fees. Pre-orders are included. Taxes are extra. Chargezen pricing.
Plan your move from Fast Bundle
Check your data, billing dates and launch plan before you switch.
Talk through your move- 01
List your offers
Write down the Fast Bundle offers, bundles and rules that perform best today.
- 02
Rebuild them in CheckoutOS
Create the same offers in the cart, checkout, post-purchase and thank-you page.
- 03
Test side by side
Use A/B tests to compare results before you switch everything over.
- 04
Turn off Fast Bundle
Remove the old offers so customers only see one set.
Why brands switch to Chargezen
Unified Platform
Run AI agents, texts and email, upsells, creators and subscriptions from one place.
AI-Powered
AI agents answer customers, follow up and handle everyday busywork for your team.
Clear Pricing
See prices and usage costs, billed monthly or yearly.
Ready to switch from Fast Bundle?
See the products, prices and setup help that fit your brand.
Common questions
Fast Bundle is $19/month up to $1,000 in monthly bundle sales, $49 up to $3,000 and $139 up to $10,000, with Auto Bundle Detection at $49/month more (checked October 16, 2026). CheckoutOS is $99/month at any volume.
