The decision in context
The same routine works for every fold
To fold a stroller, take your child out and set the brake first. Keep your fingers clear while the frame closes. Then check that the fold has locked before you lift it. After you open it again, check that every lock is engaged before your child rides. The buttons, and the order you use them in, differ by model. That part comes from your own manual.
The three manuals checked for this guide show the folding steps mainly as drawings, not written steps. So this guide does not list button-by-button instructions. Find the folding pictures in your manual, or the maker’s own instructions for your exact model.
- Before: child out, brake on, other children kept away.
- During: hands and fingers clear of moving parts.
- After folding: check the lock, then carry it the way your manual describes.
- After unfolding: check that all locking devices are engaged.
- Over time: keep the folding parts clean and dry, and look for damage.
Before you fold: child out, brake on
Bugaboo’s checked non-US Butterfly 2 manual says to remove the child from the carry cot or seat before folding the stroller. That is the first step, every time.
Next, stop the stroller from rolling. Joolz’s international Aer² manual says to always apply the brakes when the stroller is not moving. Ergobaby’s North American Metro 3 manual says to always lock the parking brake when the stroller is stopped.
Other children count too. Bugaboo and Ergobaby both say to keep the child away when unfolding and folding. Joolz says you and your children should be safe from moving parts when unfolding, folding, and adjusting.
Bags and accessories are a model-by-model question. Check what your manual says about the basket and any attached accessories before you fold.
During the fold: keep fingers clear
A stroller frame has joints that close against each other. Ergobaby’s manual says to keep hands and fingers, especially of children, clear of moving parts during folding and unfolding to prevent finger entrapment. That means a finger caught in a closing gap. Joolz’s manual gives the same kind of warning about finger entrapment.
Joolz calls the Aer² fold a “One-Hand Fold” and says you can fold, steer, and adjust with just one hand. Bugaboo says the Butterfly 2 folds in a second. Ergobaby lists one-handed folding for the Metro 3. These are the makers’ descriptions. We did not fold or time any of these strollers.
The exact order of buttons and handles is different on each model. The Joolz manual names an “(un)folding button” in its parts list, but the steps themselves are drawings. Follow the pictures in your own manual. If a step is unclear, ask the manufacturer instead of guessing.
After folding: check the lock before you lift
Joolz’s Aer² manual says that once the stroller is folded, you should make sure the auto folding lock is engaged before carrying it. It also warns that the stroller can unfold without using the activation button when shaken. So look at the lock first, then lift.
For the carry itself, Joolz says to use the carry strap to transport the folded stroller. Ergobaby says to always use the carry bag, sold separately, when carrying the Metro 3 for long periods. Bugaboo’s manual names a carry strap in a warning: do not leave it on the seat.
Ergobaby’s manual also says not to carry or lift the stroller with a child in it. That applies whether the stroller is folded or open.
The checked Bugaboo and Ergobaby documents do not describe a separate fold lock. That does not mean your model has none. Your manual shows how your stroller stays closed.
After unfolding: check every lock before use
All three manuals say to make sure all locking devices are engaged before use. These are the latches that hold the frame in its open shape. Check them each time you unfold, before your child goes back in.
Opening the frame moves the same joints as closing it. Joolz and Ergobaby both name unfolding in their finger warnings, so keep hands clear on the way out too.
Bugaboo’s manual says to always apply the brake when loading or unloading your child. It also says to check before each use that the harness works and the handlebar is locked. Ergobaby says to lock the parking brakes and check that the stroller is stable before you put your child in or take your child out.
How small the three checked strollers fold
Joolz lists the folded Aer² at 20.9 × 17.3 × 9.2 in. Bugaboo lists the folded Butterfly 2 at 17.6 × 9.6 × 21.8 in. Ergobaby lists the folded Metro 3 at 22 × 17.3 × 9 in.
The makers do not list the three numbers in the same order, so do not compare only the first figure in each list. These are the makers’ figures, not our measurements.
Bugaboo calls the Butterfly 2 fold IATA-compatible. It also tells you to check with your airline before you travel, because policies vary. A small fold is a starting point, not a boarding promise.
For a closet or car trunk, measure the opening and the space behind it. Then compare all three numbers with your own measurements.
Keep the folding parts clean and checked
Ergobaby’s Metro 3 manual says to keep the handlebar and folding mechanisms free of abrasive grime and moisture. Abrasive grime means grit, like sand. If those parts get wet, it says to dry them with a soft cloth.
Bugaboo’s manual describes a soft brush for sand and dirt in the mechanisms and sliding tubes of the frame. It also says to routinely inspect and maintain your stroller.
Joolz’s manual says to regularly inspect the stroller, chassis (the frame), and accessories for signs of damage and tear. Ergobaby says not to use the stroller if any part is damaged, broken, torn, or missing.
If a lock or the fold stops working the way your manual shows, contact the manufacturer. This guide does not give repair advice.
The documented details
| Feature | Joolz Aer² | Bugaboo Butterfly 2 | Ergobaby Metro 3 |
|---|---|---|---|
| Fold as the maker describes it | One-hand, one-second | One-second ultra-compact fold | One-handed folding |
| Folded size (maker) | 20.9 × 17.3 × 9.2 in | 17.6 × 9.6 × 21.8 in | 22 × 17.3 × 9 in |
| Lock check named in the manual | Auto folding lock before carrying; all locks before use | All locking devices before use | All locking devices before use |
| Can unfold when shaken | Yes, per manual | Not stated | Not stated |
| Carry help named | Carry strap | Carry strap (named in a warning) | Carry bag, sold separately |
| Mechanism care named | Inspect regularly for damage | Brush sand from mechanisms | Keep free of grime and moisture |
A few questions, answered.
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Sources and method
We checked the sources below on November 2, 2026. Product dimensions and features are manufacturer-reported. Our recommendations are editorial interpretations of that information; we have not tested these products. Amazon supplies current listing titles, images, and retailer links when available. Those listings are not evidence of performance.
- Joolz US: Aer² model specifications
US product page; folded dimensions use the detailed specification block, which differs slightly from rounded marketing copy.
- Joolz: Aer² international manual
Joolz manual, Feb 2025 international edition, copy hosted by a retailer; says fabrics are machine washable, unlike the US product page.
- Bugaboo US: Butterfly 2 specifications
Butterfly 2 US listing, not Butterfly 2 Plus or the original Butterfly.
- Bugaboo: Butterfly 2 user guide
Non-US edition; differs from the US page on the sun canopy and basket.
- Ergobaby: Metro 3 weight and dimensions
Use the folded measurements and accessory-free weight; no unfolded measurements are inferred.
- Ergobaby US: Metro 3 product and model options
Standard and Deluxe are separate packages. This selection uses Metro 3 Standard.
- Ergobaby: Metro 3 North American manual
NA edition; maintenance, cleaning, damage warnings, and approved parts.