The hashtag #KamiTidakTakut has emerged in the aftermath of Thursday's attacks.
A common meme, of a peace sign with a Jakarta landmark in its centre, was adapted from an image used on social media after the Paris attacks.
Where the Eiffel Tower stood in the Paris version, this shows Indonesia's National Monument.
It stands in the centre of Jakarta as a symbol of the country's struggle for independence. It is a famous landmark and popular meeting point in the city.
A photograph that appeared to show a satay seller continuing to work at his stall after blasts were heard was circulated widely online.
Some Twitter users wrote alongside it: "Fear is not in our dictionary."
The photograph was first uploaded to a local social media site, with a comment saying the stall was 100m away from the site of the bombs, which had happened two hours earlier.
The satay seller has since been interviewed by Indonesian media.
Another popular hashtag was #JakartaBerani, which can be translated as "Jakarta is Brave".
Soon after reports started to filter through on Thursday morning (local time) that explosions had been heard, Twitter users started to use the hashtag #PrayforJakarta. It is not a new hashtag. It had previously been used in cases of severe flooding, but was used again as people from Indonesia and around the world shared their sympathy for the city.
Aulia Masna, a technology blogger in Jakarta, said the morning's events had shown Indonesians used Twitter as much as ever for updates.
He tweeted that "everyone flocks to Twitter", and the microblogging site was not being "abandoned" by Indonesians as some had said.
People in Jakarta have responded defiantly to the attacks in their city by posting the Indonesian phrase for "We are not afraid" on Twitter.