Verify SD card capacity before a camera shoot

A card labeled with plenty of storage can still run out of room sooner than expected. Some counterfeit cards report a larger capacity than their flash memory can actually hold. During a camera shoot, that can mean missing, damaged, or unreadable footage discovered only after the card is full.

Test the card before relying on it. TooLab’s Fake USB & SD Check fills a USB drive or SD card with test data, then reads it back to check its real capacity. The test can help you decide whether the card is trustworthy for the shoot, but it does not test recording speed or guarantee that it will work in your camera.

Check the card before the shoot

1. Open the Fake USB & SD Check on a computer in Chrome or Edge. This tool works in those browsers on a computer. Other browsers may offer a reduced version or no access to the card.
2. Copy any files you need from the card to another location. A full-capacity check writes test data to the selected media. Do not run it on a card with footage, photos, or other files you need to keep.
3. Connect the empty card using a card reader, then follow the tool’s prompts to select it and run the capacity check. Make sure you have selected the card, not another drive.
4. Let the tool finish writing and reading the test data. Do not remove the card or disconnect the reader while the check is running.
5. Use the result to decide whether to trust the card. If the check fails, do not use it for important footage. If it passes, format it in the camera before the shoot and record a short test clip.

Plan extra time for a large card because the check needs to write and read data across it. A card that holds hundreds of gigabytes can take a while to test, especially through a slow reader or USB connection.

What the result means

The test writes and reads the expected capacity

This is evidence that the card can store and return data across the tested space. It is a useful check against a card that claims more storage than it has. It does not prove the card can sustain your camera’s recording speed, will last for years, or is genuine from a particular brand. Test it in the camera as well.

The test cannot verify all the claimed space

Do not rely on the label’s full capacity for a shoot. A counterfeit card may report a large size to a computer even though it has much less physical storage. When writing goes beyond the real capacity, older data can be overwritten or new files can become corrupted. Retire the card from important use and contact the seller if it was sold as new.

The computer shows slightly less space than the label

A small difference is normal. Card labels usually use decimal gigabytes, while some computer screens show gibibytes, a different unit. Formatting also uses some space for file-system information. A 128 GB card may therefore appear as roughly 119 GiB before the camera creates its own folders. That small unit difference is not, by itself, proof of a fake card.

The card passes but the camera runs out early

Capacity is only one factor. High-resolution video, high frame rates, RAW photos, and long bursts can use space quickly. Check the camera’s remaining-time or remaining-shot estimate after formatting, and compare it with the length of the shoot. Keep a spare card rather than planning to fill the first one completely.

Plan how much space the shoot needs

Use your camera’s recording estimate as the practical guide. It accounts for the selected resolution, frame rate, and recording mode better than a general estimate. Change those settings and the available recording time can change sharply.

For a rough video estimate, recording time in minutes is approximately storage in GB multiplied by 133, then divided by the video bitrate in Mbps. For example, 128 GB at 100 Mbps gives about 170 minutes before file-system overhead and other camera data. This is only an estimate: variable bitrates and camera settings affect actual file sizes. Use verified usable capacity rather than the label’s number if the card has failed a capacity check.

For photos, the number that fits depends on image size and format. RAW files are usually larger than JPEGs, and some cameras save both at once. Take a few sample photos in the planned mode, check their file sizes, and use the camera’s remaining-shot estimate to leave enough room for the session.

What to do if the card looks unreliable

1. Keep important footage off the card. If it has already been used, copy anything readable to a separate drive before testing or formatting. Do not use a questionable card as the only copy of a shoot.
2. Check the card and reader. Reseat the card, inspect the contacts for dirt or damage, and try a different reader or computer. A reader problem can interrupt a test, so repeat it only after confirming the card is empty and the connection is stable.
3. Run the capacity check again if the first run was interrupted. A disconnect or computer sleep can prevent a complete result. Keep the computer awake and do not unplug the card until the check finishes.
4. Replace a card that fails a complete check. Do not try to fix a capacity mismatch by formatting the card. Formatting changes how the card is organized, but it cannot add missing flash memory or make a false capacity claim true.
5. Test the replacement in your camera. Format it using the camera’s own format option, record a short clip in the settings you plan to use, then play it back. This checks basic compatibility and recording behavior that a browser test cannot confirm.

What this test cannot tell you

A capacity check does not measure sustained write speed, which matters when a camera records high-bitrate video or rapid bursts. Check the camera maker’s card requirements for the recording mode you plan to use, and test a short recording in that mode. A card can have its advertised capacity and still be too slow, worn, or unreliable for a particular camera.

After testing, keep a second copy of the shoot’s files on a separate drive before reusing or clearing the card.