One key obstacle in fabricating efficient flexible and printable optoelectronic devices is the absence of ideal flexible transparent conductors with superior optical, electrical, and mechanical properties. Here, high-performance flexible transparent conductors are demonstrated using ultrathin (<10 nm) doped silver films, which exhibit an averaged visible transmittance of 80% without any antireflection coating, sheet resistance less than 20 Ω sq, and mechanical stability over 1000 bending cycles. The conductor is prepared by doping silver with an additive metal (e.g., nickel, copper, titanium, chromium), and its various properties can be readily tuned by either using different doping metal species or controlling the dopant concentration. Centimeter-size, flexible polymer light-emitting diodes are fabricated using a nickel-doped silver-based electrode, and the devices exhibit 30% enhanced current efficiencies compared to their indium tin oxide counterparts, invariant emission spectra at large viewing angles, and operational stability for over 1200 bending circles. In addition, 6 in. flexible low-emissivity coatings are demonstrated using a copper-doped silver-based conductor, which transmit 85.2% of the visible light while rejecting over 90% of the infrared radiation beyond 1250 nm.