Thousands of people who attended a rehearsal on Monday were asked not to circulate images or videos.
Danny Boyle, the ceremony’s artistic director, reportedly addressed the audience to “save the surprise”.
About 62,000 are set to attend the opening ceremony at the Olympic Stadium in Stratford, east London, on Friday.
The event is expected to be watched by an audience of billions worldwide.
Olympic organizers LOCOG said the technical rehearsal for the opening ceremony “went very well”.
“The reaction from the attendees has been overwhelmingly positive on social media and crucially they are still helping us to save the surprise for the rest of the nation on Friday,” it said.
People who attended the rehearsal reported that the hashtag “#savethesurprise” was emblazoned on giant screens inside the Olympic Stadium.
It later trended globally on micro-blogging website Twitter.
In other developments:
• Transport for London has apologized after people leaving the rehearsal were delayed getting home because the Central Line, which serves Stratford, was partly suspended
• The British Olympic Association says it has asked triple jumper Phillips Idowu to supply details about his injury ahead of the Games after the 2008 Olympics silver medallist pulled out of the Great Britain athletics team’s training camp
• On Tuesday, Heathrow is set for its busiest day for Olympics so far as it prepares to handle about 217,000 passengers, including some 1,200 athletes and coaches and more than 3,000 other Games-related arrivals
• Motorists have faced long queues on routes where pre-Olympics modifications have been made to road layouts
• And the Olympic torch is travelling from Kingston, in south west London, to Ealing, west London, as it continues its tour of the host city’s 33 boroughs.
Most people who attended the rehearsal appeared to obey the appeal for secrecy, although there have been reports of some images being posted on the internet before being removed shortly after.
Many took to Twitter to show their support after the rehearsal.
“I am now sitting on my seat in the Olympic Stadium. But I shall #savethesurprise and not tweet details of the ceremony. Sorry,” tweeted Dan McNeil.
And many gave positive reviews of the ceremony on the website.
One person who was in the audience, Pete Hendrick, tweeted: “If you’ve got plans Friday night, cancel them. Opening ceremony is out of this world. Danny Boyle, I salute you.”
Chris Golds, another audience member, said the event was “breathtaking” and “awe inspiring”.
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