The difference between RAM and storage
Two separate gigabyte figures face you when buying a device: one is RAM, the other storage. Both look like memory, yet they do entirely different jobs, and knowing which one is short is the key to choosing the right device.
Short answer
RAM is the fast, temporary memory holding the data a device is working on at that moment; its contents are erased when the device is switched off. Storage is the permanent space where your files live. Too little RAM makes a device slow at multitasking; too little storage leaves no room for new files and apps.
The desk and the filing cabinet
The most established comparison is this: storage is a filing cabinet and RAM is a desk. All your files sit in the cabinet (storage); when you start a task, the relevant ones are brought out onto the desk (RAM), and when the task is done they go back into the cabinet.
The wider the desk, the more files you can work with comfortably at once. With a small desk you constantly fetch and put away, and the work slows. With a small cabinet there is nowhere to put new files even when the desk has room. The two problems are independent of each other, and so are their solutions.
RAM: fast but temporary
RAM (random access memory) holds the data the processor is using at that instant. It is many times faster than a drive; open applications, the document you are editing and background tasks all live in RAM. There is a price for that: it is temporary. When the device is switched off or the power is cut, everything in RAM is erased.
That is why an unsaved document is lost in a power cut: the document was still on the desk, not yet put away in the cabinet. The “save” button is the command that moves data from RAM to permanent storage.
When RAM fills up, the system is not left helpless; it makes room by moving less-used data temporarily to the drive. But because the drive is far slower than RAM, that move is felt immediately: a page reloading when you return to an old browser tab, or hesitation when switching apps, are the signs of the desk overflowing and the cabinet being called on.
Storage: the permanent archive
Storage is the permanent space where your files are preserved without electricity: photos, videos, applications and the operating system itself all sit there. Two main types are seen in today's devices: traditional hard disk drives (HDDs), which are cheaper and higher in capacity, and solid state drives (SSDs), which are far faster and silent.
Much depends on the type of storage, from how long the device takes to start up to how quickly applications load; two computers of the same capacity can feel entirely different when one has an SSD. The safety of the files in storage is a separate matter; for that, see the backup guide.
Some phones allow storage to be extended with a memory card, which gives a photo and video archive practical breathing room. Cloud storage offers similar relief: rarely used files can be moved to the cloud to free space on the device. Neither method, however, replaces the speed and quality of the main storage on which applications are installed.
Which one is short: the symptoms
The typical symptoms of insufficient RAM are these: noticeable slowdown with many tabs or apps open, stalling when switching between applications, and background apps restarting frequently. Insufficient storage looks different: “not enough space” warnings, being unable to take photos, being unable to install updates.
As a rough starting point: 8 GB of RAM is enough on most computers for basic use, while 16 GB gives comfort for heavy multitasking; on phones, 128 GB of storage has become a common lower limit today. Needs vary from person to person.
What this means in practice when buying
The shopping consequence of the distinction is clear: a single gigabyte figure printed large in an advertisement can mislead, so check RAM and storage separately. On phones neither can usually be increased afterwards; on computers, some models allow RAM and the drive to be upgraded, which is an option that extends the device's life.
Cloud storage can ease the pressure on storage by providing extra room for files; but no cloud service can take the place of RAM, because working speed depends on the device's own memory.
When storage gets tight, try a clear-out before buying: removing unused applications, emptying the downloads folder, deleting the media piling up in messaging apps and backing up photos to thin them out on the device often frees gigabytes. On most systems the storage screen already shows in detail what is taking up how much room.
Frequently asked questions
Why does switching a phone off and on again help?
Restarting empties RAM; accumulated background tasks are cleared and the system makes a clean start. The files in your storage are unaffected by this.
Can RAM be added later?
Not on phones; on computers it depends on the model. Some laptops and desktops have RAM slots open to upgrading, while in others the memory is soldered to the mainboard. It is worth asking about this flexibility when buying.
Why does a device slow down when storage is full?
The operating system needs free space for temporary files and updates, and those operations become difficult as space runs out. Leaving a portion of storage free (around 10–15 per cent) is a common recommendation.
Does more RAM always mean faster?
Only up to a point. More than you need makes no difference in everyday use; speed is a whole formed with the processor and the type of storage. A balanced configuration matters more than one high figure.
This guide draws on introductory computer hardware sources and on the technical specification documents published by device manufacturers.