Where is Doraemon's spare fourth-dimensional pocket?

Okay, regarding Doraemon's spare pocket, let me explain. This setting is actually mentioned in both the original manga and the movies!

Doraemon's Spare Pocket: The Little Secret Hidden in the Closet

Simply put, Doraemon's spare fourth-dimensional pocket is hidden in the closet where he sleeps, usually placed under his pillow or beside his futon.

This detail appears in many places, most notably in the movie "Doraemon: Nobita's Secret Gadget Museum". At that time, the bell-shaped pouch around Doraemon's neck (which is also his main pocket) was stolen by Phantom Thief DX, leaving Nobita and the others frantic. Finally, Doraemon remembered he had a spare one. He then rummaged through his sleeping closet and pulled out an identical spare pocket from under his pillow.

Spare Pocket ≠ Another Storage Space

Here's a crucial point to understand:

The spare pocket and the main pocket access the same fourth-dimensional space.

Think of it as "another door" leading to the same vast warehouse.

The main pocket is the one on Doraemon's belly, his usual "front door" to the warehouse.
The spare pocket, kept in the closet, is the "back door" used in emergencies.

Therefore, gadgets pulled from the spare pocket are exactly the same as those from the main pocket. He doesn't have two separate inventories of gadgets. If his main pocket is lost, he just needs to take out the spare pocket to continue using all his gadgets.

Why Have a Spare?

This is actually a very reasonable sci-fi setup, much like how we keep backups of important things. It's primarily used in the following situations:

Cleaning and Maintenance: The fourth-dimensional pocket gets dirty too! There are scenes in the manga and anime where Doraemon sends his pocket for cleaning, during which he uses the spare.
Loss or Theft: As seen in the "Secret Gadget Museum" plot mentioned above, this is the most critical scenario. Without the spare pocket, Doraemon would truly become a (relatively) ordinary blue robot.
Accidental Damage: Although the pocket is sturdy, if it were somehow damaged in an unusual situation, the spare pocket would be immediately available.

So, this spare pocket is essentially Doraemon's "ultimate safety net". While it rarely makes an appearance, it's incredibly important in critical moments! It just sits quietly in the closet, waiting for the moment it's needed.