To help you find the exact build or verify your support status: What is your ? Do you have an active FortiCare subscription ? Are you seeing specific performance issues or bugs ?
Never download FortiOS images from unofficial forums or "free" mirrors. These files can be injected with backdoors that compromise your entire network. Choosing the Best Firmware Version
Navigate to Download > Firmware Images . Select FortiGate as the product and browse the folder structure to find the 100D specific builds. Fortigate 100d Firmware Download BEST
To ensure you are getting an authentic, untampered image, you should only use official sources.
The FortiGate 100D is a legacy workhorse in the Fortinet lineup. Before you search for a download, you must verify the support status: To help you find the exact build or
Use the MD5 or SHA256 checksums provided on the Fortinet support site to verify the integrity of your downloaded file.
Once this date passes, technical support and firmware access via official channels typically cease. Never download FortiOS images from unofficial forums or
This is the primary and only recommended source. Log in at ://fortinet.com using your credentials.