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SanDisk 256GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-256G-GN6IN


(13 customer reviews)
Last updated on August 28, 2023 5:30 pm Details
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  • Great choice for compact to mid-range point-and-shoot cameras
  • Quick transfer speeds up to 120MB/s(1) to backup those moments (1)(For 32GB-256GB): Up to 120MB/s read speed, engineered with proprietary technology to reach speeds beyond UHS-I 104MB/s, require compatible devices capable of reaching such speed. Write speed lower. Based on internal testing; performance may be lower depending on host device, interface, usage conditions and other factors. 1MB=1,000,000 bytes.
  • Up to 32GB to store tons of pictures and even more Full HD video(2) 1GB=1,000,000,000 bytes. Actual user storage less. (2)Full HD (1920×1080) video support may vary based upon host device, file attributes, and other factors. Visit the SanDisk Video Knowledge Base for more information.
  • Exceptional video recording performance with UHS Speed Class 1 (U1)(5) and Class 10 rating for Full HD video (1080p)(2). (5)UHS Speed Class 1 (U1) designates a performance option designed to support real time video recording with UHS enabled host devices.
  • Compatible devices: SanDisk SD UHS-I card reader

Specification: SanDisk 256GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-256G-GN6IN




‎SanDisk Ultra SDXC UHS-I card

Item model number


Item Weight

‎0.08 ounces

Product Dimensions

‎1.26 x 0.94 x 0.09 inches

Item Dimensions LxWxH

‎1.26 x 0.94 x 0.09 inches

Processor Count



‎Western Digital Technologies, Inc.

Country of Origin


Is Discontinued By Manufacturer


Date First Available

‎September 28, 2020

Photos: SanDisk 256GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-256G-GN6IN

13 reviews for SanDisk 256GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-256G-GN6IN

3.9 out of 5
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  1. M. L. Bush

    I use these in my hunting cameras and they work fine. Records excellent pictures and video. Nothing negative to say.

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  2. Allan Bantick

    When used in Browning Recon Force 4k trail cameras, these SanDisc discs created corrupt mp4 and jpg files in up to 50% of images taken. The same problem did not arise in the Browning when using most other makes of disc although I did have the same problem with some super-cheap discs, which these ScanDiscs are most definitely not. However, these SanDiscs worked OK when tested in a Cannon SX71 camera and a Bushnell E3 trail camera and in general PC usage. Am in discussion with Browning on the subject. I hope this is helpful.
    Allan Bantick

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  3. Sarah

    This is a genuine SanDisk sd card and held files to its full size without file loss.

    It writes at about 30mbps on my PC. The ‘up to 120mbps speed’ claim on the packaging is READ SPEED not write speed. This is a game all card manufacturers play on us. (To get a card with high write speeds you need to pay much more – look into the write details not the headline claimed ‘speed’.)

    This is a great card for the price and if you just want to take photos or Full HD video it will be fine. For 4K video or high bit-rate, 50fps FHD you should use a U3 rated card instead.

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  4. P. Wolf

    I’ve had bad experiences with SD cards in the past, generally when I use them for an extended period of time, rewriting them several times. That’s why I decided to move to a one and done approach, once I fill an SD card it gets offloaded to an external drive for use, and the card goes into storage as a backup.
    This SanDisk 128GB SD card however started to exhibit problems before the card was even full however with significantly degraded read and write speeds after 3/4 of the card was filled.
    To prevent a total loss of data the contents were backed up and the card was retired.
    I shoot lots of photos, several thousand a year, and I purchase lots of SD cards, anecdotal evidence from my experience would suggest that I have a higher failure rate with SanDisk SD cards as compared to the other name brand manufacturers I use, Lexar, PNY, Sony, and Samsung.
    Moving forward I’ll be sticking with them and skipping SanDisk.

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  5. spsweeney

    The original SD Card was a standard SD Card with a 2Gb capacity, which held approximately 3 years of data. This SD Card is 32GB, or the equivalent of 16 standard SD Cards. I copied the data from the original SD Card onto this card taking up approximately 2GB, leaving 30GB, or approximately the capacity of 15 standard 2GB SD Cards. Using the figure of 3 years/2GB SD Card x 15 2GB SD Cards = 45 years. So this new 32GB SDHC card can hold an additional 45 years of CPAP data. I hope to be with us when I have to upgrade to a SDXC card. I had an old SD card reader which couldn’t write to SDHC cards, so I purchased a UGREEN SD Card Reader, which can read and write SD, SDHC, SDXC cards, both standard and micro cards.

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  6. User654378

    This supposedly is the newer model of the Sandisk Ultra series. It claims to deliver “up to” 120MB speeds which when compared to the previous model, it’s about 20MB faster. (120MB vs 100MB not a big difference). I cant compare the two since I only have the newer model.

    Anyways using the benchmark application, the read speed I got was around 90MB/s. Which is great but less than advertised. Ironically though, if you look at other reviewers with “Sandisk Extreme cards up to 170MB”, they are only getting about the same read speed as this card does. (Unless theirs are counterfeits.)

    In my real life testing, it took about 10 minutes to transfer a 6.5GB file from my laptop to this SD card. Compare that to my old Sandisk USB stick, this SD card is light years ahead! Another good thing about this sd card is that the performance is sustained.

    On the other hand, the write speed would be too slow for filming in 4K. I recommend you to spend extra on cards with faster write speeds if filming is your use primary case etc…

    Using the Lumix DSLR alongside this SD card is not a problem! Everything runs smooth as it should, just don’t expect to film in 4k as I’ve said, the write speeds are too slow for that.

    All in all, I’m somewhat satisfied with this purchase. It’s cheap. Offers reliable read speed and is good enough for my purpose. It’s also sold by Amazon and not by other potentially fake sellers so that’s assuring 🙂

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  7. TractorDeerHunter

    I have been using these cards in my trail cameras for several years, and have purchased more as I increase the amount of cameras that I own. I wasn’t having any problems until the past couple of orders. Now, when I go to format the cards, after reviewing the photos, it takes a very long time to eventually say that there is not a card inserted, or that it can’t be accessed. I go back to my older cards and have no problem. Much time is wasted, and many pictures have been missed, because the cards have not taken any pictures. This is very frustrating.

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  8. David Yirrell

    I have always found SanDisk Memory Cards to be reliable, and have so far never let me down. I have used them in my DSLR cameras for more than 10 years and now in a wild life or ‘trail camera’ with the same outcome. However it is worth noting that some equipment has a limitation of the memory size that it can address so always check before ordering.

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  9. Frank

    Tested memory card as soon as I received it to make sure it supported the full stated capacity and it was not a counterfeit card. Everything checked out and the memory card has so far worked without issue.

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  10. Kamen

    As other reviewers have noted, the write speed of this card is horrible. I bought it to replace an older SD card and the SanDisk performed much worse! Here are the comparative benchmarks for both:

    * SanDisk 64GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-064G-GN6IN

    Warning: Only 60872 of 60874 MByte tested.
    Test finished without errors.
    Writing speed: 21.9 MByte/s
    Reading speed: 86.9 MByte/s
    H2testw v1.4


    * Samsung PRO UHS-I 64GB SDXC Memory Card – MB-SG64D/AM

    Warning: Only 61028 of 61029 MByte tested.
    Test finished without errors.
    Writing speed: 74.4 MByte/s
    Reading speed: 85.0 MByte/s
    H2testw v1.4

    This may be fine for some uses, but is unsatisfactory for photo/video cameras – one of the main targets of SanDisk memory cards. My Canon 7D Mark II shoots long bursts of RAW images at 10fps and this write speed is insufficient.

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  11. Mia N.

    I got my SanDisc 32 Gigabyte Ultra SD Card through the mail in perfect condition, I inspected the packaging and labels to verify if I had received a “fake” memory card and everything was intact as well as the accuracy of the labels. The packaging was very tightly packed in with the cardboard and clamshell packaging melted together, the memory card is secured in a clamshell packaging with a plastic film that covers the would be exposed section of the clamshell packaging inside the cardboard packaging, the memory card labels, icons, and finished paint for memory card’s sticker is exactly the same as the images online for the product. I had used an external USB memory card reader with 3.0 USB Ports and used the H2w_Test software to verify if the memory card has accurate memory information, storage capacity, as well as read & write speeds. The test had no errors that had ever occurred and I have exactly 29.7 Gigabytes which is what your going to get, read & write speeds were about 20 Megabytes on average for me but I’m using an external 3.0 USB SD card reader, so it”s fine.

    Overall, the memory card works as advertised,
    I’m a very happy customer!

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  12. Box of Possums

    What more is there to say other than that which the title of this review already conveys? It’s an sd card. Transfer speeds are decent enough. It does what it claims. Can’t fault it.
    I should buy more face masks, underwear, etc, adorned with magnificent possums or comical weasels – they’re far easier to review with humour than a memory card that does exactly what a memory card needs to.

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  13. tjs114

    Our vehicles use these cars for their operating system and navigation maps, and I don’t feel comfortable reusing them more than 3 times for that since the cards get very hot in automobiles, and get a lot of read/write activity.

    So, catching these on sale as a 3-pack works out to getting 3 cards for the price of 2, and I haven’t gotten fake SanDisk 3-packs, unlike singletons. SanDisk cards have been the most reliable for me with full size SD cards, but I’ve had more luck with Samsung microSDs.

    I honestly can’t figure out the SanDisk naming convention because they spam several names with different speeds on the same name (for example, these Ultra cards are labelled 120MB/s, but I see other Ultras at only 80MB/s and higher end cards at only 100MB/s.

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    SanDisk 256GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-256G-GN6IN
    SanDisk 256GB Ultra SDXC UHS-I Memory Card – 120MB/s, C10, U1, Full HD, SD Card – SDSDUN4-256G-GN6IN
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