There are many commercial software, some come with certain equipments. Others, like PROFEX, are free and open source Rietveld refinement software. I prefer to use Rietveld method for X-ray diffraction data analysis.
I am not expert I can not say best. But from my experince I agree with Esmaeil x'pert Highscore is simple and good for phase identification. In addition origin can help you to analyze the data if you know your card as well and can calculate several things such as crystal size, crystallite index and so on.
Actually, the answer is not that simple if you work with general powder diffraction patterns, quantitative analysis, then most XRD free software can do that, e.g. GSAS (1 & 2), MAUD, PROFEX-BGMN, Fullprof, JANA2006, Rietan-FP, Rietica, POWDER CELL, and many more. But if you need a specific issue, then one/some software is much easier to handle than others, perhaps even purposely make for that particular issue, e.g. MAUD is great for texture, Fullprof for Magnetic phase, PM2K for advanced microstructural analysis (domain size, dislocation, faulting, APB etc.), JANA2006 for modulated structure, RIETAN-FP for MEM analysis, etc.
Hi Heydar Haghghipour ! It depends what kind of XRD output you need ? If you need to study the phase of your sample then you may use simply "search match" in case of finding crytallite size and crystallinity you need to plot that data in origin to get that. hope it will help.
Dear Niqab Khan, the diffractogram is not a simple graph. This Origin is also not free software. Find the attached file if you want to dive into crystal size in particular, crystallinity is another thing.