The Half Dome Cable Route hike runs from the valley floor to the top of the dome in 8.2 mi (13 km) (via the Mist Trail), with 4,800 ft (1,460 m) of elevation gain. The length and difficulty of the trail used to keep it less crowded than other park trails, but in recent years the trail traffic has grown to as many as 800 people a day. The hike can be done from the valley floor in a single long day, but many people break it up by camping overnight in Little Yosemite Valley. The trail climbs past Vernal Fall and Nevada Fall, then continues into Little Yosemite Valley, then north to the base of the northeast ridge of Half Dome itself.

The final 400 ft (120 m) ascent is steeply up the rock between two steel cables used as handholds. The cables are fixed with bolts in the rock and raised onto a series of metal poles in late May (the poles do not anchor the cables). The cables are taken down from the poles for the winter in early October, but they are still fixed to the rock surface and can be used. The National Park Service recommends against climbing the route when the cables are down or when the surface of the rock is wet and slippery. The Cable Route is rated class 3, while the same face away from the cables is rated class 5.


The Cable Route gets crowded on the weekends
The Cable Route can be crowded. In past years, as many as 1,000 hikers per day have climbed the dome on a summer weekend, and about 50,000 hikers climb it every year.

Since 2011, all hikers who intend to ascend the Cable Route must now obtain permits before entering the park when the cables are up between May and October. Permits are checked by a ranger on the trail, and no hikers without permits are allowed to hike beyond the base of the sub-dome or to the bottom of the cables. Hikers caught bypassing the rangers to visit either the sub-dome or main dome without a permit face fines of up to $5,000 and/or 6 months in jail.

Backpackers with an appropriate wilderness permit can receive a Half Dome permit when they pick up their wilderness permit with no additional reservation required. Rock climbers who reach the top of Half Dome without entering the subdome area can descend on the Half Dome Trail without a permit.

The top of Half Dome is a large, flat area where climbers can relax and enjoy their accomplishment. The summit offers views of the surrounding areas, including Little Yosemite Valley and the Valley Floor. A notable location to one side of Half Dome is the "Diving Board", where Ansel Adams took his photograph Monolith, the Face of Half Dome on April 10, 1927. Often confused with "the Visor," a small overhanging ledge at the summit, the Diving Board is on the shoulder of Half Dome.

From 1919 when the cables were erected through 2011, there have been seven fatal falls from the cables. The latest fatality occurred on September 5, 2019.

Lightning strikes can be a risk while on or near the summit. On July 27, 1985, five hikers were struck by lightning, resulting in two fatalities.

The Cable Route was added to the National Register of Historic Places in 2012.
Without quoting directly from the text give me a summary of the half dome hike.
The half dome hike is 8.2 miles long with 4800 ft elevation gain. This hike can be done in a single long day or in two days by camping overnight in Little Yosemite Valley. The trail goes past Vernal and Nevada waterfalls, continues to Little Yosemite Valley and then to the half dome itself. The final 400 ft of the hike involves a steep ascent up the rock using the two steel cables fixed with bolts in the rock. The cables are put up between May and October and it is not recommended to climb the route when cables are down since the surface can be wet and slippery. All the hikers to half dome are required to obtain permits which are checked by a ranger on the trail. Hikers caught bypassing the rangers without permits are subject to penalties.