A lock on a travel backpack does one specific job: it buys time. Fabric can be cut, and anybody who tells you a padlock makes a backpack secure is selling something. But almost all theft from a bag in transit is opportunistic — a few seconds, one hand, behind you, while the bag is on your shoulders or hanging off a chair. A lock makes that a two-handed job that takes real time and attention, and that is usually all it takes for someone to pick a different bag.
The problem is that backpacks are badly designed for locking, and most guides skip straight past the reason. So start here, with the check that determines whether any of this is even possible on the bag you own.
First, count the sliders
Open your main compartment and look at the zipper. There are two possibilities and they lead to completely different answers.
Two sliders that meet in the middle. This is what you want. The two pulls can be threaded onto one lock, which means they cannot separate, which means the zipper cannot be opened. On a clamshell travel backpack this is unusually effective, because the single long zipper running around three sides is the onlyway into the main compartment — lock those two sliders and the bag is closed. The clamshell design is covered in what is a clamshell backpack.
One slider that parks at one end.There is nothing to lock it to. This is the design on most cheap daypacks and on a surprising number of mid-priced ones, and it is why “lockable zippers” is a feature worth looking for rather than something you can assume. Your options are a thin cable or a cable tie through the pull hole and around a nearby strap anchor, so the slider physically cannot travel, or to decide that compartment is unsecured and keep nothing in it you would mind losing.
The three methods, in order of how much they do
1. Lock the sliders to each other. A small padlock or a wire loop through both pull holes. Cheap, fast, and the method that actually prevents the common theft. Keep the lock small: a heavy padlock swinging off a zipper abrades the fabric around it over a few hundred miles.
2. Use the bag’s own anchor.This is the quiet advantage of a purpose-built anti-theft bag, and it is better than a padlock in three ways. The pulls clip to a fixed hidden point under a flap, so there is no dangling hardware, nothing to lose, no added weight, and — the part people miss — no visible signal that the bag is worth opening. Pacsafe builds this into the Metrosafe X alongside its eXomesh slashguard panels and RFID-blocking pockets; Travelon builds locking hardware into the Metro at a third of the price.
3. Lock the bag to something fixed.A thin cable lock through a strap anchor and around a bed frame, the luggage bar above a train seat, or a locker bar. This is a different problem from the first two: it protects the bag’s location, not its contents, and it is the right tool for a hostel dorm or an overnight train where the bag will be out of your sight for hours. The failure mode is anchoring to something that lifts — a cable around a chair leg protects nothing at all.
The cheap version of all three, worth knowing because it works: cable ties. A single zip tie through two sliders takes four seconds to fit, costs nothing, is impossible to undo quietly, and tells you instantly if the bag has been opened. Carry a few and a nail clipper. It is not a lock, it is a tamper seal, and on a bag going into a hold that is arguably the more useful of the two.
What a lock does not do
Three limits, stated plainly, because the whole value of this method is knowing where it stops:
- It does not stop a blade.Any fabric panel can be cut, and locking the zipper does not change that. If a cut bag is a real risk on your route, that is what slash-resistant construction is for — whether you need it is the subject of are anti-theft backpacks worth it.
- It does not secure the outer pockets. Water-bottle pockets, front stash pockets and the top grab pocket are almost never lockable. Treat every one of them as public space.
- It does not protect a bag you have left somewhere. A locked bag on a restaurant floor is a locked bag that leaves with somebody. The cable method above exists because locking the zipper and leaving the bag are two different decisions.
Locking a backpack you have to check
The failure mode changes completely once the bag goes into the hold. Theft is the smaller risk; the conveyor is the bigger one. Loose shoulder straps, a dangling hip belt and compression webbing are exactly what baggage systems catch, and an exposed harness is the most common way a travel backpack comes off a belt damaged.
So the order is: stow the harness first, lock second. Packs with a zip-away harness panel make this easy — Osprey’s published specification for the Sojourn 45 names a stowaway harness, backpanel and padded hipbelt, all of which disappear behind a cover. On a pack without one, cinch every strap as short as it goes and tuck the belt. Then lock the main zipper, using a lock you are willing to lose, and assume the bag may be opened for inspection along the way.
Two things never go in the checked bag regardless of how well it is locked: spare lithium batteries and power banks. The FAA requires them to be carried on rather than checked, and TSA says the same — lithium-ion power banks and portable chargers must be in your carry-on. The full routine is in how to pack electronics for travel and the rest of the checked-backpack problem is in can you check a backpack as luggage.
Three bags where the locking is built in
You can lock almost any two-slider zipper with a padlock, and if you already own a good travel pack that is the cheapest fix on this page. If you are buying, these three have the hardware designed in — which means no dangling padlock and no advertisement. Prices come from the live price layer with the date they were read.
#1Best locking day bag: lockable pulls plus slash-resistant panels
Pacsafe Metrosafe X 20L Anti-Theft Backpack
The real anti-theft pick — not a hidden pocket, but a system: slash-resistant fabric, locking zippers and RFID-blocking pockets. A 20L daypack for pickpocket-heavy cities where you want to stop worrying about your bag. Priced accordingly.
Strengths
- +Slash-resistant paneling and lockable zipper pulls — actual security, not just a hidden pocket
- +RFID-blocking pockets for cards and passport
- +Comfortable, low-key 20L daypack
Trade-offs
- −Security hardware adds weight and cost versus a plain daypack
- −20L is a day bag, not a travel main-bag
| Capacity | 20 L |
|---|
| Weight (empty) | 1.87 lb |
|---|
| External dimensions | 17.7 x 11.8 x 5.1 in |
|---|
| Carry-on fit (our read) | Personal-item sized |
|---|
| Laptop sleeve | 16 in |
|---|
| Material | 750D recycled polyester, eXomesh slashguard |
|---|
| Warranty | Pacsafe 5-year limited warranty |
|---|
Fit note. This is what 'anti-theft' should mean: slash-resistant fabric and locking zippers, not a marketing sticker. Overkill for a quiet trip; exactly right for a crowded market or a night train.
Specs read from the product listing, on September 7, 2026. “Not published” means the maker does not state that figure.
#2Best for locking your main bag: the same system on a 35L travel pack
Pacsafe Venturesafe EXP35 Anti-Theft Travel Backpack
The rare bag that is a genuine one-bag carry-on AND a genuine security system. At 35L it's sized to clear a sizer, and it brings Pacsafe's slash-resistant construction and locking zippers to the main travel pack rather than just a daypack. It costs what a premium travel pack plus a security bag would cost — which is roughly what it is.
Strengths
- +Anti-theft construction on a full 35L travel pack, not just a daypack
- +35L clears carry-on sizers more comfortably than a 40L
- +Locking zippers and RFID-blocking pockets built in
Trade-offs
- −The most expensive way to buy 35L of capacity
- −Security hardware adds weight you carry on every trip, theft risk or not
| Capacity | 35 L |
|---|
| Weight (empty) | Not published |
|---|
| External dimensions | Not published |
|---|
| Carry-on fit (our read) | Carry-on compliant |
|---|
| Laptop sleeve | Not published |
|---|
| Material | Not published |
|---|
| Warranty | Not published |
|---|
Fit note. 35L is the right capacity for this bag's job: big enough for a week with cubes, small enough that you are not fighting a sizer while also carrying security hardware. If you only want anti-theft for day trips, the 20L Metrosafe X is far less bag and far less money.
Specs read from the product listing, on August 11, 2026. “Not published” means the maker does not state that figure.
#3Best value: real locking hardware and an RFID pouch, cheaply
Travelon Anti-Theft Metro Backpack
The sensible middle of the anti-theft market: real locking hardware and an RFID-blocking pouch at roughly a third of a Pacsafe's price. You give up the full slash-resistant paneling, so treat it as strong deterrence rather than a vault — which, for most trips, is the honest amount of security to buy.
Strengths
- +Locking hardware and an RFID-blocking pouch at a mid-market price
- +Low-key everyday styling that doesn't read as a tourist bag
- +Light enough to work as a personal item or day bag
Trade-offs
- −Deterrent-grade, not the full slash-resistant system a Pacsafe gives you
- −A day bag — it is not a one-bag main travel pack
| Capacity | Not published |
|---|
| Weight (empty) | Not published |
|---|
| External dimensions | Not published |
|---|
| Carry-on fit (our read) | Personal-item sized |
|---|
| Laptop sleeve | Not published |
|---|
| Material | Not published |
|---|
| Warranty | Not published |
|---|
Fit note. Anti-theft is a spectrum, not a yes/no. This sits in the middle: locking zippers and RFID shielding stop the opportunist, while a determined thief with a blade is the Pacsafe's problem to solve. Most travelers only ever need the middle.
Specs read from the product listing, on August 11, 2026. “Not published” means the maker does not state that figure.
The Metrosafe X is the one to buy if the bag you most want secured is the one at your feet all day — and at 17.7 x 11.8 x 5.1 in it also works as a personal item on a flight. The Venturesafe EXP35 is the rarer thing: locking zippers and slash-resistant construction on a full 35L main travel pack, so the security is on the bag holding your clothes rather than on a daypack. It is also the most expensive way to buy 35 liters, which we say on best 35L travel backpacks. The Travelon is the sensible middle: locking hardware and RFID shielding without Pacsafe money, and deterrent-grade rather than vault-grade, which for most trips is the honest amount of security to buy.
The habits that matter more than the lock
If you do only three things, do these: wear a daypack on your front in a crowd or on transit; never hang a bag on the back of a chair; and split your cards and cash so that losing the bag is expensive rather than trip-ending. A lock is the backup to all three, not a replacement for any of them.
We have not tested these bags and we do not own them — everything above is mechanics and what each maker publishes about its own hardware. Our method, and what we refuse to claim, is in how we choose.