Memory card or USB drive not working? Stop before the next write

The card comes back from a camera job in Warsaw, Windows asks to format it, macOS says the disk is unreadable, or a USB stick from the office shows 0 B. At that moment the most valuable action is boring: stop writing to the device and protect the current state.

SD, microSD or USB asks to format, disappears or shows 0 B

Cancel the format prompt. Do not take more photos, record more video, copy test files or save recovered files back to the same card. Flash media can fail after an interrupted write, unsafe removal, camera battery loss, controller fault, worn NAND cells or a bent connector.

The files may still exist even when the directory looks empty. The danger is that each new write can reuse blocks that still contain the only copy of photos, video, documents or project material.

The first step with a memory card or USB drive

If there is no visible damage and the device is not hot, one controlled test with a reliable reader or port is reasonable. If the same prompt returns, capacity is wrong, folders open slowly, or the device appears and disappears, stop testing.

• Cancel format, repair and initialisation prompts.
• Do not run CHKDSK, Disk Utility repair or recovery scans on the original if it is unstable.
• Do not put recovered files onto the same card or USB drive.
• Write down the last normal use: camera model, computer, transfer app and error message.

Most common reasons flash media stops working

Logical failures often follow unsafe removal, interrupted recording, accidental deletion or file-system damage. Physical failures include cracked SD cards, bent USB plugs, broken solder joints, liquid damage, overheating, controller failure and degraded NAND memory.

• Physical damage, the riskiest category: cracked housing, bent USB connector, broken SD card, failed controller or damaged NAND after a drop, liquid or power surge. Symptoms include no detection, no LED, heat or repeated disconnects.
• Logical damage, common and often recoverable: file-system errors after unsafe removal, power loss or a camera write interruption. Symptoms include format prompts, RAW/0 B capacity, empty folders or a device that asks to be repaired.
• User mistakes: accidental formatting or manual deletion. In many of these cases, data remains on the card until new files overwrite the old blocks.

Professional formats such as CFexpress, XQD and CFast add another layer: high write speed, camera-specific folder structures and readers that may report failure poorly. For these cases, see CFexpress, XQD and CFast data recovery.

What to do before recovery starts

The first moves should reduce writes to zero. In "please format" situations, flash media data recovery works from a controlled read path and lowers the risk of overwriting material.

• Stop using the media immediately. Every connection attempt, especially formatting, increases the risk of overwriting data.
• If the damage is physical, do not connect it. A bent connector or hot device can short or damage electronics further; put it in a safe box.
• If the problem is logical, make a bit-level create a sector image before recovery. Use a read-only method such as ddrescue or a lab imaging workflow, then scan the copy, not the original.
• Do not install recovery programs onto the same system disk or flash media. Use another drive in the computer.
• Label the carrier and write down the circumstances: "removed during copying", "coffee spill", "camera stopped recording". This helps the technician choose the safest option.

When media is stable enough, a technician can create a read-only create a sector image before recovery and recover files from that copy. When it is unstable, visibly damaged or heating, repeated scans at home can reduce the number of readable blocks.

Useful case details include capacity, brand, file type, camera or device model, whether the failure happened during recording or copying, and whether any format or repair attempt has already been made.

When to choose a professional laboratory

Choose lab diagnosis when the card or USB drive is the only copy, when the files are client work, when the connector is bent, when the device shows no media, or when every reader reports a different capacity. For a service route, start with memory card data recovery.

• The carrier has visible physical damage: cracked, flooded, burnt or bent.
• After connection it does not react at all: no LED, no heat, no capacity.
• Software recovery attempts have already failed.
• The data is irreplaceable and there is no room for experiments.

A sensible diagnosis should separate logical damage from controller or physical failure and explain whether chip-off, controller work or standard imaging is realistic.

How do you choose a good laboratory?

• Ask directly about experience with the exact medium type: for example SanDisk USB drives, Sony camera cards or professional SD media.
• Require standard diagnosis and a transparent quote before paid work starts; the data recovery pricing page helps set expectations.
• Check reviews and case studies from similar flash-media cases.
• Make sure confidentiality is covered; private photos, company files and client data may require an NDA.
• Avoid miracle offers. Professional flash recovery with microscopy, soldering stations or NAND work has a real cost.

In the laboratory, depending on the fault, specialists may repair a connector, stabilise electronics, desolder memory chips and read NAND directly before reconstructing the original file structure.

Emergency plan summary

• Prevention: regularly copy files from removable media to a computer or cloud and use the eject function.
• Reaction: when failure appears, stop and decide whether the problem looks physical or logical.
• Action: for logical issues, clone the carrier and scan the clone. For physical damage, do not experiment; contact the laboratory.
• Decision: if the data is important and you are not sure, a specialist consultation is safer than risky testing.

Stop using the device, prevent writes, keep it physically safe and prepare the symptom history. If it is a memory card from a shoot, do not reinsert it into the camera to see whether it starts working again.

If this is part of paid photo or video work, protect future jobs with a repeatable copy routine. The related workflow is described in backup workflow for photographers and videographers.

Temporary USB glitch or real flash failure?

A simple reader or port issue usually disappears after one reliable test on another computer. A real media failure tends to repeat: format prompts, 0 B capacity, heat, disconnects, unreadable folders or long freezes during copy.

If behaviour changes from attempt to attempt, treat the media as unstable. Unstable flash memory is not a good place for experiments.

When experiments no longer make sense

Stop experimenting when the device contains the only copy, was dropped or bent, heats up, reports 0 B, disconnects under load, or makes recovery software freeze before the scan even reaches file previews.

For realistic expectations before diagnosis, see data recovery cost ranges. For damaged professional media, also compare CFexpress, XQD and CFast recovery and flash media recovery.

What if it is the only card or USB drive with important data?

Do not try to pull one time-sensitive file again and again from the original device. The better route is to preserve the current state, describe symptoms through contact with the laboratory, check how recovery pricing works and work from a controlled image or a lab process designed for failing flash media.

See also: cards, flash media and backup planning

• Why formatting first is a bad recovery plan
• How to choose backup storage for photos and projects
• Memory card data recovery