To what extent are the hadiths authentic, and how can one determine which of them are not fabricated?

Allah has guaranteed the preservation of His religion, embodied in the Quran and the Sunnah (definition). He has prepared for their preservation trustworthy scholars who were able to distinguish between weak and fabricated hadiths. A student of knowledge can identify these hadiths by referring to books of biographies (rijal), al-jarh wa al-ta'dil (discrediting and accrediting narrators), and books on hadith (definition) terminology. They have also been compiled in specialized works such as "Al-Ilal Al-Mutanahiyah" and "Silsilat Al-Ahadith Ad-Da'ifah wa Al-Mawdu'ah" by Al-Albani.