How to Video (Chrome)
Steam Guide (Please rate likes :D Thanks!)
Chrome Tampermonkey extension

How to use :
0. Install Tampermonkey on your broswer and enter the below script.
1. Ctrl + C to copy your steam activation key.
2. Open Steam Key Online Activation
3. Ctrl + V to paste your steam activation key to the input box. Your product will be automatically activated.
4. Repeat...

Script to copy to Tampermonkey