It's a poorly-kept secret that Spotify wants to go public, but when, exactly? Apparently, the answer is "soon." Axios has learned that Spotify quietly filed initial public offering documents with the US Securities and Exchange Commission in late December. The company has declined to comment, but the insiders claim that Spotify has chosen to go with a direct listing, saving costs and preventing shareholders from losing money. The timing suggests that Spotify could launch its IPO in the first quarter of 2018, although whether or not that happens is up in the air -- the streaming service may have serious legal hurdles to clear.