Turbotax Online is "free to start." You only pay when you are ready to file (cost based on the forms you use) so if you don't like the online program, you can simply clear your data and go to another web site.
The desktop software (installed on your PC or Mac) must be purchased, but has a 60 day money back guarantee.
The mobile version is free to download, but it is not a separate tax app; it connects to the online version, so it is free to start and you pay when you are ready to file.
If your income is less than $39,000, you may qualify for the IRS freefile program which is free no matter what forms you need. Turbotax dropped out of this program but you can find a list of current providers on the IRS web site.
