For analog television, modifying the size of the captions text is not possible. Analog television EIA-608 does not give the viewer the option to change any of the characteristics of the captions, such as size, color or font. The only person able to change the color and position of the text on the screen is the captioning operator. Font type and size cannot be changed.
The standard which defines captions characteristics for digital television is the EIA-708. The viewer has an opportunity to modify some of the captions characteristics, such as the color of the text and the background color, or the type and size of the font. However, this is possible only if the STB or the television allows these changes to be made. Currently, there is not a regulation requiring all television sets or STBs to include these options.