Each heading below carries an exact error string, so you can match your terminal output against the page and jump straight to the fix. Most of these have simple causes, a shell that was never initialized, an installer quirk, permissions damage left by sudo, and one of them, the terms-of-service gate, is recent enough that plenty of working pipelines met it as a surprise. If conda is not recognized after installing Miniconda, the first two sections are yours.
conda: command not found
You ran the installer on Linux or macOS, typed conda and got conda: command not found back. Two causes cover almost every case: either the installer never ran conda init (batch installs with the -b flag skip it on purpose), or it did run and you're still inside the old shell session, whose PATH predates the installer's edit to your rc file.
This fix works even when the shell knows nothing about conda, because it calls the activation script by its full path:
source ~/miniconda3/bin/activate
conda init
Close the terminal and open a new one, or reload in place with source ~/.bashrc on bash, source ~/.zshrc on zsh (the macOS default). The prompt should now begin with (base) and conda --version should answer. On a fresh server where you'd rather do the whole sequence from the top, download through first environment, the guide to install Miniconda on Ubuntu runs it end to end.
How to find the Miniconda path
The commands above assume the default prefix. If the installer was pointed elsewhere with -p, or someone else set the machine up, first confirm where Miniconda lives:
ls ~/miniconda3 ~/opt/miniconda3 /opt/miniconda3 2>/dev/null
Whichever of those shows bin and pkgs folders is your install. If none do, hunt for the conda binary across your home directory:
find $HOME -maxdepth 4 -name conda -path "*/bin/conda" 2>/dev/null
Take the folder two levels up from the hit (/home/dev/tools/miniconda3, not the bin/conda part), source its activation script from there and run conda init. From then on conda info --base prints the install path whenever you need it.
'conda' is not recognized as an internal or external command, operable program or batch file.
The Windows version of the same problem, with a twist: it's by design. The Miniconda installer keeps conda off the system PATH unless you tick the option it explicitly warns against, so a regular Command Prompt has never heard of the program. Nothing is broken.
The supported entry point is the Anaconda Prompt (miniconda3) shortcut in the Start Menu, which loads conda for that session, and from that prompt you can wire conda into your everyday terminals permanently:
conda init cmd.exe
conda init powershell
Run one or both, close every open terminal, reopen. PowerShell users sometimes meet a follow-up error where the new window refuses its profile because "running scripts is disabled on this system"; that's the execution policy blocking the profile script conda init just wrote, and allowing locally created scripts clears it:
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
The whole Windows setup, installer screens included, is in the guide to install Miniconda on Windows.

