The Tool Desk
Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A file name extension is the suffix conventionally placed after the final period in a filename. In expenses.xlsx, the extension is xlsx (often written as .xlsx). It can help an operating system or application identify a file type or choose an app, but it is only a naming clue: it does not prove what the file contains, and changing it does not convert the file.
Where the extension appears in a filename
A conventional filename has a name followed by a period and an extension: report.pdf. The name is report; the extension is pdf. People often include the period when referring to an extension, as in “the .pdf extension.” Microsoft uses expenses.xlsx to illustrate the same distinction: Microsoft’s guide to common Windows file extensions.
Extensions are conventions, not a required part of every filename. Windows filename rules treat the extension as optional and separate it from the base name with a period: Microsoft Learn’s Windows file-naming guidance. A filename may also contain more than one period, as in archive.tar.gz. In such cases, the suffix a person or program treats as the extension can depend on the tool and its conventions; it is safest to describe the exact suffix you mean.
What a file extension does
An extension can help software decide how to handle a file. Depending on the operating system and application, it may be used to associate the file with a type, display an icon, or select an application that can open it. Windows uses filename-extension associations, while Apple describes extensions as indicators of file type and the apps that can open files: Apple’s guide to showing or hiding filename extensions on Mac.
#1 Best Overall
- USB-C 2-in-1 storage OTG: The Lexar JumpDrive Dual Drive D40E features USB Type-A and Type-C connectors in a slim, portable form factor for easy device compatibility
- Transfer speeds up to 100MB/s: Based on internal testing, performance may vary depending upon the host device, interface, and usage conditions. 1MB=1,000,000 bytes
- Plug and Play: Widely compatible with USB Type-C smartphones, tablets, laptops, Macs, and traditional Type-A devices, no software installation required. The 360° swivel design allows for easy switching between connectors without the hassle of losing a cap
- Durable & Compact: The Lexar D40E USB memory stick features a metal enclosure, withstands temperatures from 0° to 50° C (32°F to 122°F), and is lightweight at 26g with dimensions of 70.4 x 16.9 x 11.7mm
- Security & Warranty: Securely protects files using an advanced security software solution with 256-bit AES encryption. Backed by a Lexar 3-year limited warranty
That behavior varies. Some systems or applications do not rely on suffixes, and a suffix may be incorrect. MDN notes that file extensions are not guaranteed to be accurate and are not meaningful to every operating system: MDN’s explanation of MIME types and file extensions. So an extension is useful for naming and app selection, but it is not a universal or definitive description of a file.
What the extension cannot tell you
The suffix alone cannot prove that the file’s contents match its apparent format. A file named report.pdf might not contain PDF data if it has been mislabeled. The visible filename is one clue; the data inside and other metadata can provide different evidence about the file type.
Rank #2
- High-speed USB 3.0 performance of up to 150MB/s(1) [(1) Write to drive up to 15x faster than standard USB 2.0 drives (4MB/s); varies by drive capacity. Up to 150MB/s read speed. USB 3.0 port required. Based on internal testing; performance may be lower depending on host device, usage conditions, and other factors; 1MB=1,000,000 bytes]
- Transfer a full-length movie in less than 30 seconds(2) [(2) Based on 1.2GB MPEG-4 video transfer with USB 3.0 host device. Results may vary based on host device, file attributes and other factors]
- Transfer to drive up to 15 times faster than standard USB 2.0 drives(1)
- Sleek, durable metal casing
- Easy-to-use password protection for your private files(3) [(3)Password protection uses 128-bit AES encryption and is supported by Windows 7, Windows 8, Windows 10, and Mac OS X v10.9 plus; Software download required for Mac, visit the SanDisk SecureAccess support page]
MIME media types are another way software identifies or communicates file types. In its legacy Windows Media guidance, Microsoft recommends using the MIME type in the file header for identification: Microsoft Learn’s file-type identification guidance. A MIME type and a filename extension are related clues, but they are not the same thing.
Changing an extension is not converting a file
Renaming notes.txt to notes.pdf changes the filename, not the data inside. The file does not become a PDF just because its suffix says .pdf. Microsoft explicitly warns that changing an extension does not convert a file: Microsoft’s guide to common Windows file extensions.
Rank #3
- What You Get - 2 pack 64GB genuine USB 2.0 flash drives, 12-month warranty and lifetime friendly customer service
- Great for All Ages and Purposes – the thumb drives are suitable for storing digital data for school, business or daily usage. Apply to data storage of music, photos, movies and other files
- Easy to Use - Plug and play USB memory stick, no need to install any software. Support Windows 7 / 8 / 10 / Vista / XP / Unix / 2000 / ME / NT Linux and Mac OS, compatible with USB 2.0 and 1.1 ports
- Convenient Design - 360°metal swivel cap with matt surface and ring designed zip drive can protect USB connector, avoid to leave your fingerprint and easily attach to your key chain to avoid from losing and for easy carrying
- Brand Yourself - Brand the flash drive with your company's name and provide company's overview, policies, etc. to the newly joined employees or your customers
To make a file a different format, use an application or conversion process that actually rewrites or exports the contents in that format. Renaming is appropriate when correcting a filename, not when changing the underlying file format.
Why an extension may not be visible
Some interfaces hide filename extensions even when the files still have them. On macOS, for example, Finder can show or hide extensions through its settings. Apple’s guide explains how to control that display: Show or hide filename extensions on Mac. If you do not see a suffix in a file list, it may be hidden rather than absent.
Rank #4
- GOOD VALUE PACKAGE - 1 Pack 32GB Memory Stick USB 2.0 Flash Drives with great cost performance and high quality.
- BIG CAPACITY - The available capacity: 29.10GB-29.8GB, You can save the data of movies, music, photos, designs, programs, manuals, handouts in a high speed.Good performance in digital data storing, transferring and sharing with families, friends, workmates, clients and machines.
- EASY TO USE & PLUG AND WORK - Support windows 7 / 8 / 10 / Vista / XP / 2000 / ME / NT Linux and Mac OS, Compatible with USB2.0 and below.
- TWISTTURN DESIGN & EASY CARRY - The metal clip rotates 360° round the ABS plastic body which with rubber oil skin feeling finish. The capless design can avoid lossing of cap, and providing efficient protection to the USB port.
- WARRANTY & SUPPORT - SIMMAX logo is laser printed on the USB connector surface, our products are of good quality and we promise that any problem about the product within one year since you buy.
When creating a new extension
If you are defining a new public file type, check whether the extension is already associated with another application before adopting it. Microsoft Learn advises checking the Internet Assigned Numbers Authority (IANA) MIME database for existing associations: Microsoft Learn’s guidance on choosing a file type extension. It also recommends defining or registering a MIME type for a new public file type.
Quick Recap
Best Value
- 【16GB Flash Drive】USB flash drives with 16GB capacity, meet your needs of daily use on work, school, home and travelling for photos, music, videos, files storage and transfer. IMEASON thumb drives can be used to store different files, easy to data backup.
- 【Metal Swivel Cap Design】USB thumb drive is metal swivel cover provides extra protection for the usb thumbdrive connector, no usb drive cap to lose; keychain design makes it easier to carry without worrying lose it.
- 【Wide Compatibility】USB drive supports Windows 7/8/10/11 / Vista / XP / Unix / 2000 / ME / NT Linux and Mac OS, also Supports USB 2.0 and 1.1 ports. USB Stick support TV, desktop, notebook computer, car, audio and other device. The USB Memory Stick is your great data storage and transfer companion with traveling and working.
- 【Easy to use】usb memory stick is plug and play without any software installation. Just simply plug the Flashdrive into the port of your USB-compatible devices such as computer, laptop to start data storage or transmission.
- 【What You Get】16 GB USB Flash Drive Thumb Drive, The default format of the usb storage flash drive is FAT32.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
