CONTROL File

What are CONTROL files and how to open them

Are you having problems opening a CONTROL file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CONTROL files.

What is a CONTROL file?

A .CONTROL file is a HEC-HMS Control Specifications Data file.

HEC-HMS Control Specifications Data files store timing and configuration settings that tell the Hydrologic Engineering Center's Hydrologic Modeling System when a watershed simulation should start, stop, and how often to compute results. They are created by the HEC-HMS software as part of a project setup defining the simulation time window and computational time step.

A file of this type records the name and optional description of the control specification; a start date and start time; an end date and end time; and a time interval (also called computational timestep) for simulation and output. Dates are entered in the format day-two-digit, month three-letter abbreviation, year four digits (for example 08Feb1936) using the Gregorian calendar; times use 24-hour notation and minute precision (for example 14:15) with the requirement that start and end times align with the interval chosen.

Simulation runs use the control specification to determine when calculation begins and ends and how frequently intermediate results are computed or interpolated. If input time-series or gridded data have coarser resolution than the interval, HEC-HMS will interpolate them linearly to match the control interval. The control specification does not usually contain parameter or routing data - those belong in other project files.

Internally, the file begins with the ASCII text "Control: " at byte offset zero, and includes keywords such as LAST MODIFIED DATE, LAST MODIFIED TIME, TIME INTERVAL, START TIME, START DATE, END TIME, END DATE, and CONTROL among its content.

How to open CONTROL files

Important: Different programs may use files with the CONTROL file extension for different purposes, so unless you are sure which format your CONTROL file is, you may need to try a few different programs.

While we have not verified the app ourselves yet, our users have suggested a single CONTROL opener which you will find listed below.

Last updated: September 2, 2026

Various apps that use files with this extension

These apps are known to open certain types of CONTROL files. Remember, different programs may use CONTROL files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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