If your windows are cracked or broken, this is not just unsafe but also makes your home less comfortable to live in. You need to have broken window glass repaired as soon as possible, to prevent intruders from using your predicament to break in to your home and to keep a stable temperature on the inside. If you're window is just cracked, not broken, it's very possible to perform glass repairs on your own. However, to repair a crack in your window, you should know that different situations require different types of fixes.
Cracks on single pane windows
If you have a single pane window that has gotten cracked, you most likely have to replace the glass entirely. A crack in a single pane window means there are no other unharmed barriers to stop wind from getting through your window. It's also very difficult to repair a crack on a single pane, as these types of windows aren't as robust as double pane windows, meaning you can actually break them entirely as you're trying to repair the crack. While you're waiting for professionals coming to your house to perform the window replacement, you should place a piece of tape over the crack to prevent it from affecting the temperature inside.
Cracks on double pane windows
You should also put a piece of tape of the crack of your double pane window, as this prevents the crack from widening before you have time to repair it. A very simple repair that can prove very effective is to use clear nail polish to fix the crack. Apply many thin layers of the nail polish over the crack. Allow each layer to dry properly before applying the next one. Keep doing this until the nail polish is at the same level as the rest of the glass. Try to protect the nail polish from the wind as it's drying, as you don't want dirt and dust to stick to the polish. This can leave a dirty stripe on your window that can't be washed away.
If your window is just scratched, and not cracked all the way through, there's another simple fix you can do. Use a whitening tooth paste and a soft cloth to rub the scratch away. This is a very gentle buffer that sands the window without giving it more scratches. You shouldn't use any more abrasive buffers than this on your window as you might just end up making the problem worse. Also avoid doing this on deep scratches, as you might have to create a dent in your window glass to level the scratch.